This is a screenshot of a 3 moving objects in game mode. (cube is only rotating). They are supposed to be uniformly glowing. But this happens when they move.
They all have the same material that has a uniform emissive color, yet in game mode the emissive "jumps ahead" of the diffuse?
All objects are supposed to be uniformly white and glowing, but they show what looks like z-fighting, glitching from the emissive to the regular diffuse, happening only when moving?

The error does not occur in the editor, where all objects and their emissive work fine.

Here's a few gif's showing the issue.

Game mode / launcher:
https://gfycat.com/HeartyDangerousFlyingsquirrel

Editor:
https://gfycat.com/AssuredWhisperedGreendarnerdragonfly

Anyone know what's going on?
We've basically broken a large part of our game by updating to v. 5.3.3 with this. On top of that we're set to deliver release candidates soon.

Edit: Maybe I should add that this error appeared when we updated from 5.2.3 to 5.3.x

I have to do a follow up on this one. Any suggestions?

We need to know if there is a solution or if we need to make a work-around. We're in the final months of a commercial title, so we badly need a solution for this.