When Editing a large package in another schema (3506 lines of code) I have noticed that the syntax coloring will sometimes fail when opening then closing a string value. For example, I typed the following line of code into the package editor at line 1796. After doing so, lines 1796 - 2749 appear to be string. Line numbers 1-1795 look fine. Line numbers 2750-3506 also looked fine, strangely enough.
v_test := 'test string';
I have not been able to replicate this in smaller packages, but can every time with a large one. I do not know at what point it becomes too large, or if editing across schema's has something to do with it. I also do not know if there are certain code patterns present in packages that exhibit this behavior.