Seeing this appear on your page with no actual error message has got to be the bane of perchance users across the world 😅
It’s really opaque, and gives you nothing to go on. So you resort to commenting out whole sections of code trying to get any clue as to what the problem is.
It would really improve the experience of developing apps if there was a real message somewhere for us to see.
Can you share an example where the red error indicator isn’t shown for a syntax error? It should be shown - e.g. https://perchance.org/ktj0659v15#edit so it sounds like you’ve found a bug.
I found a case that gave me the problem just before posting, but didn’t think to save it as an example you could see. It’s definitely not happening all the time, but also it doesn’t seem to be randomly intermittent, but comes from some obscure edge case or other.
If I manage to find it again, I’ll come back to this post and reply to you again. 👍