ORA-00904: "xxxxxxxxxxxx": invalid identifier (3: 0): Warning: compiled but with compilation errors

I am working on a huge View I inherited. I was tasked with adding new columns to tables and adding them to views. The view is almost 2000 lines, it has the create section, and a union query. The field that shows up in this error message exists in the view, the underlying table, and is correct in length, spelling, etc. However, every time I try to compile it, I get the message in the title. I've checked for missing commas, parentheses, etc. and everything is there. I don't know where else to