Solved! I had two blueprints in my game, both of which were using Stereo Layers. Crucial for my VR game. I removed them from my persistent level using 4.24.3 and then the project opened normally in 4.25.1 (after the making of the copy). I haven’t tried adding the Blueprints with the Stereo Layers back in the game, but I hope it will work. More news as it breaks!