Please fix it because it does not work with webgl

Which version of UFE are you using (Lite, Basic, Standard, PRO, Source)?
Does the same error happens when you are testing it in the Unity Editor?
If the stage is a scene file, is the scene listed under your Build Settings -> Scenes In Build?

You are correct. Bug confirmed.
The issue seems to be the Fuzzy AI.

I ran multiple tests but I still don't know the exact cause for it. The current webgl version running on http://www.ufe3d.com/demo/ufe2/webgl/ seems to be running just fine, which means the issue could have been introduced by Unity 2019.

I'll keep running more tests, see if I find the cause. For now, just use the Random AI option for your WebGL build.

Not yet. The limitation is related to how WebGL works on browsers, so there is not much I can do from my end.
An alternative solution would be to reduce the amount of conditions the Fuzzy AI can handle. Under AI Editor -> Advanced Options, try disabling as many attack filters as you can for your game and see if that works.

i'm helping on a game for WEBGL, gotta see if any of this problems show up!

I have disabled all attack filters and still cannot load stages. This is a huge problem as our team bought UFE2 Source thinking we could build to web. I've also set the global editor AI settings to use Random instead of Fuzzy. Please advise.