Hi Ranger, this is probably a variation on the issue I warned about in post 3532
https://celephais.net/board/view_thread.php?id=60097&start=3532&end=3532

If the save file dates back to an earlier version of the mod, and you've added, removed or reordered a model precache since then, you now have an incompatibility between your mod and your save file. Having a DIFFERENT deterministic precache sequence causes exactly the same problem as a non-deterministic one. It's one of those inconveniences you hit more often as a developer, your save files won't have a long shelf life until the mod is stabilised. 

Hi Andrew, I didn't do a great job of explaining where I was coming from. When I read your original post my impression was you believed the problem lay in a change between the version T effectinfo.txt and the version U effectinfo.txt. I admit I might have inferred incorrectly.

The really key message I wanted to send is that the flashlight in version T is not using effectinfo.txt - so you won't be able to locate the key to non-flickering effects there; there's nothing you can port to version U. It also makes it much more likely that the problem really lies in the ENGINE rather than the mod, that custom effects aren't compatible with high frame rates.

If you're into updating the engine then you can focus the effort there. If all you can do is change the mod, then you need to find a workaround for the bug, and that usually entails some kind of compromise. Capping FPS at 72 might be the better trade-off, you'll have to weigh it up.