Maybe this will help some of you:

When I tested my game in WebGL for the first time, a gamebreaking bug occurred.

Fortunately, the error always occurred in the same place and was therefore relatively easy to narrow down:

To create delays in the game I use "Task.Delay()" instead of coroutines. Unfortunately, WebGL cannot handle threading and stops the code execution at the first occurrence.

If you have the same problem, take a look at this package, it helped me very quickly and easily: https://github.com/VolodymyrBS/WebGLThreadingPatcher