Thank you so much! Ah that's unfortunate, I'll have to optimize a bit more .. what device are you playing on?
actually a pretty beefy self-build desktop PC but in a Firefox browser.
I think you can preload the next level in the background so you only have to activate it once the player progresses. Important part is that it does not load everything in one frame. You could also try and reuse existing tiles but that is a common cause for bugs.