I have monitored this issue on my machine for several months, and when it comes up, it’s 100% reproducible. It comes up when I try to edit some specifics about already working and deployed code, code that has already had Syntax Highlighting run over it.
Just now, I tried to change the return type of a method from String to a List of a Wrapper class, but the IDE froze after I wrote “List<“ and the autocompletion added the closing bracket >. And then, when I copypasted the List including type, it again happened when I tried to wrap a for-loop around an SOQL-Query that was originally cast into a List.
Other instances where it came up was when adding an additional brackets for adding an if-clause when there originally was none. There it froze after I typed in the first bracket and tried to add the second bracket to the end of the code snippet that was supposed to be affected.
I don’t know if the Dump helps, I can also add the idea.log if necessary. However, this is becoming increasingly annoying, especially in a complex Org as the one I am working with where this regularly comes up.