I wonder if shaders needed to compile. Compiled shaders are also stored in multiple places so it would be hard to test on your end. What engine? I ask because Godot let's you export with somewhat compiled shaders
It's actually a handmade engine, so I can guarantee shaders are compiled at startup. Whatever's causing it, I'd like to get to the bottom of the poor performance. Who knows who else is experiencing something similar. You can add me on discord here: https://discord.gg/bUG8MGB7 . If you have some time to troubleshoot 1-on-1 I would greatly appreciate it!