[Ubuntu 18.04] Syntax highlight and autocompletion fail in a a specific file

Hey all,

I am experiencing an issue where PHPStorm fails to work properly with just a few specific files. Specifically, syntax highlighting is partial (sometimes it "unlocks" block of highlighted code when right-clicking something), autocompletion doesn't always work and the alt+enter menu either appears but lacks some options, or does nothing when selecting something like "Initialize properties" in a constructor. I tried invalidating all caches and restarting, but it won't fix the issue. I even tried uninstalling PHPStorm and deleting the .config/JetBrains, but the problem won't go away.

I am running an updated PHPStorm 2020.2 with just a few plugins (Symfony support, .env, editorconfig, Material Theme UI, PHP Annotations). I really can't figure out out how to start debugging this issue. I'm working on a sizeable project with a few thousand indexed files, but the problem appears with just a few specific ones (which aren't even that big, the one I've currenly open is about 240 lines long).

I have a screenshot showing the issue but I'd rather not upload it unless striclty necessary (it's not extremely sensitive data, but it's still private-ish).

Thanks!