This is on Mac (Apple Silicon). Sometimes† upon Build and Run (I'm using Nova if it matters) a line like this...
if badVariableName then
will cause the Simulator to beachball, requiring a Force Quit. Nova's "Stop" button is grayed out, and the Run button is non-functional if you try it again. This doesn't happen on app launch, but rather when the line in question is executed.
No error message or console output appears, making it tough sometimes to track down which script has the problem.
† "Sometimes" means that if a line causes the issue, it will always do so... but there are also cases where a similar issue doesn't happen (the "if" simply evaluates to false) and I haven't spotted the pattern.
It happens about once a week to me, because it can result from a simple typo (or copy-paste-o). Or if I rename/remove a variable and forget that a second script also references it.
I hate to mention it since I've been trying to make a simple reproduction case and have failed to. But for what it's worth, I saved a copy of my messy project-in-progress that exhibits the issue on a certain a line. If anyone at Panic wants to wade into that swamp, I can provide it! I have marked the specific line.
(This definitely happened in both SDK 1.11 and 1.12. Not sure if it did before that.)