Yes, I have this problem too but with the 4.0.2 update it’s gotten better, at least it feels it happens less often, usually warnings, and I haven’t needed to reboot the device to get it unstuck (relaunching app is enough).
When it does get stuck I’ll do one or both of these things in either order
- Intentionally add a space to break code around where it’s stuck then delete the space. This triggers the compiler to start working again and hopeful clears the hang up.
- With the preview/Canvas panel open, at the top it says “App Preview”. Tap on that show show a menu and choose “Restart” or “Delete Data and Restart”. This will get the compiler to try again.
If neither of those work (usually happens with a warning about a variable that’s no longer in my code) then I have to restart Playgrounds and that’s always rectified things since 4.0.2.
You can also send feedback that this needs improving (open a project, tap top-right circle icon with 3 dots inside, select “Send Feedback” from menu). I don’t understand the technical problem with it getting stuck but a button to force a more complete recompilation I think would help.