"MOVETYPE_PUSH with a non bsp model" is this fixable?

So if I make monster corpses pushable it will cause this error?

I know shubnigurrath caused this sometimes... 

I think you misunderstand MOVETYPE_PUSH. It's not to make a thing be pushable, it's designed for things like doors and platforms that do the pushing. Don't make corpses MOVETYPE_PUSH, or anything else that isn't a BSP object for that matter.

Yes, the teleport train is MOVETYPE_PUSH without being a BSP object, but that's why it sometimes crashes! It was a bad idea, probably done in a hurry to get Quake out of the door.

You can read some more on the issue here, but bear in mind that the fix discussed on the page is an engine-level fix. If you're writing a mod that doesn't prescribe which engine to use, you can't benefit from this.
https://www.quake-info-pool.net/q1/qfix.htm#movetype_push 

Basically it's overall working but
the key issues are
it never seems to stick on world (it otherwise behaves properly more or less), and thus the arming and stick sounds never play. Also even if it doesn't stick the arming sound never plays

besides that it properly triggers on enemies, bounces off doors & enemies etc, and works more or less...

I've been working on this for 9+h and can't figure it out!

void() ProximityBomb =
{
local entity head;
local float blowup;

if (vlen(self.spawnmaster.velocity)>0)
{
ProximityGrenadeExplode();
self.think();
return;
}
if (time > self.delay)
{
mine_disarm();
self.think();
return;
}


self.touch = SUB_Null; //new
self.owner = world;
self.takedamage = DAMAGE_YES;
head = findradius(self.origin, PROX_MINE_RADIUS); //sensor radius
blowup = 0;

while (head) //what to look for
{

// Don't detonate on players or other mines
if ((head != self) && (head.health > 0) && (head.flags & (FL_CLIENT|FL_MONSTER)) && (head.classname != self.classname) && (head != self.lastvictim)) //(head.classname != "player"))
{
blowup = 1;
}


traceline(self.origin,head.origin,TRUE,self);
if (trace_fraction != 1.0)
blowup = 0;


if (blowup==1)
{

ProximityGrenadeExplode();
self.nextthink = time + 0.5;
return;
}
head = head.chain;
}
self.nextthink = time + 0.25;
}; 

void() ProximityArmed = //new
{
sound(self, CHAN_WEAPON, "weapons/proxarmed.wav", 1, ATTN_NORM);
self.think = ProximityBomb;
self.nextthink = time + 0.25;
};



void() ProximityGrenadeTouch =
{
if (other == self || other == self.owner) //|| other == self.owner
{
sound (self, CHAN_WEAPON, "weapons/proxbounce.wav", 1, ATTN_NORM); // bounce sound
return;
}

if (pointcontents(self.origin) == CONTENT_SKY)
{
remove(self);
return;
}
// Don't collide with other mines
if (other.classname == self.classname)
{
sound (self, CHAN_WEAPON, "weapons/proxbounce.wav", 1, ATTN_NORM); // bounce sound
self.movetype = MOVETYPE_BOUNCE; // Add this line
return;
}


// Check if it's a brush entity (like doors)
if (other.movetype == MOVETYPE_PUSH) //|| other.solid == SOLID_BSP
{
sound(self, CHAN_WEAPON, "weapons/proxbounce.wav", 1, ATTN_NORM); // bounce sound
self.movetype = MOVETYPE_BOUNCE; // Add this line
return;
}

if (other.flags & FL_CLIENT) //user disarm mine
{
//self.solid = SOLID_NOT;
mine_disarm();
//remove(self);
return;
}

if ((other.takedamage == DAMAGE_AIM || other.solid == SOLID_TRIGGER || other.flags & FL_MONSTER )) //don't det on monsters || other.flags & FL_CLIENT
{
sound(self, CHAN_WEAPON, "weapons/proxbounce.wav", 1, ATTN_NORM);
//self.movetype = MOVETYPE_BOUNCE;
T_Damage(other, self, self.owner, 1);
//self.think();
return;
}


self.movetype = MOVETYPE_TOSS;
if (self.state == 1)
return;

if (vlen(other.velocity) > 0)
{
ProximityGrenadeExplode();
self.think();
return;
}

else
{

sound (self, CHAN_WEAPON, "weapons/proxstick.wav", 1, ATTN_NORM); // bounce sound
self.movetype = MOVETYPE_NONE;
setsize (self, '-5 -5 -5', '5 5 5');
self.state = 1;
self.spawnmaster = other;

self.velocity = '0 0 0';

// Start arming sequence
self.think = ProximityArmed;
self.nextthink = time + 2;

self.touch = SUB_Null; //new
self.solid = SOLID_NOT; //new
}
}; 

void() ThrowProxMine =
{
float x;

// Check if enough time has passed since last throw
if (self.last_mine_time > time - 1.5)
return;

// Check if player has enough ammo
if (self.ammo_rockets2 < 1)



local entity missile; //, mpuff;

self.currentammo = self.ammo_rockets2 = self.ammo_rockets2 - 1;
self.last_mine_time = time; // Update last throw time

sound (self, CHAN_BODY, "zombie/z_shot1.wav", 0.8, ATTN_STATIC);

self.punchangle_x = -2;

missile = spawn ();
missile.owner = self;
missile.lastvictim = self;
missile.movetype = MOVETYPE_TOSS;// MOVETYPE_BOUNCE;
missile.solid = SOLID_BBOX;
missile.classname = "proximity_mine";
missile.takedamage = DAMAGE_YES; //DAMAGE_NO;
missile.health = 2;
missile.state = 0; //not armed

// set missile speed
makevectors (self.v_angle);


if (self.v_angle_x)
missile.velocity = v_forward*400 + v_up * 200 + crandom()*v_right*10 + crandom()*v_up*10;
else
{
missile.velocity = aim(self, 10000);
missile.velocity = missile.velocity * 400;
missile.velocity_z = 200;
}
missile.avelocity = '100 400 100';


missile.angles = vectoangles(missile.velocity);

missile.touch = ProximityGrenadeTouch;
// set missile duration
missile.nextthink = time + 2; //min time until mine can explode from enemy
missile.think = ProximityBomb; //arm
missile.th_die = ProximityGrenadeExplode;
missile.delay = time + 90; // time until mine auto disarms

setmodel (missile, "progs/proxmine.mdl");
setorigin (missile, (self.origin) + (v_forward * 0) + (v_right * -17) + '0 0 10');

setsize (missile, '-4 -4 -4', '4 4 4');

}; 

The difficult part with your ProximityGrenadeTouch function is there are so many return statements which MIGHT end the function, and the bit of code that makes it stick to the wall is at the very end.

I would recommend you add some dprint statements to the function after each "checkpoint" - each place where the function has avoided a branch that contains a return. Then you can check how far execution gets through the function when you throw one against a wall, and deduce which exit is being taken unexpectedly. Two tips
a) pull down the console as soon as the bomb hits a wall for the first time, as you'll get a huge pile of debug messages if you let it bounce all over the shop first
b) remove the debug statements once you have solved the mystery, or they will be a pain in future 

Another issue is... is it possible to dynamically spawn monsters real time via impulse? (like half life's impulse 76)

I tried adding the monster's model precache to void () worldspawn, void () StartFrame , but i keep getting "host error pf precache can only be done in spawn functions?" 

StartFrame runs every frame! If you put a precache in there, you will hit the error for a late precache just about as fast as it's possible to hit it. Stick to worldspawn and you'll have a better time.

But as long as you time the precaches correctly (always on frame 0, and never afterwards), you can spawn monsters dynamically, in essentially the same way as creating a rocket or grenade. One small catch is that you can't update the total_monsters count after the first frame - so your monster kills can go over 100% unless you ensure that dynamically spawned monsters don't count for the kill count.

Another tricky wrinkle to deal with is where to place the monster so that it isn't stuck. Usually that's the responsibility of the mapper! One thing's for sure, you'll have to come up a compromise, and here's the proof: imagine that we make a map that's just a box 8 units larger than the player. It's physically impossible to successfully spawn a monster into that map. 

One other thing to warn you - don't ever randomise your precaches! Imagine you had some plan to randomly select one monster which your impulse spawns for the duration of the map, and you make the selection in frame 0 then precache just the assets for the selected monster. This exposes you to an interesting bug!

The bug arises when you save and load the game. In particular when you load the game, the engine:
1) Runs the first few frames of the map as if you had started from scratch
2) Reads the entity states from the save file and shuffles everything around to match it
The point of 1) is mainly to precache everything again. But second time round you might roll a different number on the random monster table and precache different models. Things may start showing up with the wrong models, or if you are less lucky the whole thing just crashes.

The only way to avoid this problem is to make the precache sequence entirely deterministic. If you're married to the random spawnable monster idea, you might have to precache the models for all the options, even if only one is ever used at a time.

And there are other more subtle ways to hit this error. Imagine you have an entity which you only allow a 50% chance of manifesting, randomised on each map load. Even if you have so many of this entity that one spawns every time, random variation might change the order in which models are first precached, as the first manifestation may occur before or after other fixed entities. Changing the order of precache messes up which models appear after a save is reloaded.