I have a class that compiles and runs OK, but IDEA flags it red with a 'Class must implement method or be declared abstract' error. The class extends one superclass and implements two interfaces. The method it complains about is implemented in the superclass of the superclass (grandparent), and is declared in the interface implemented by the grandparent. All legitimate code, and no method name clashes or conflicts.
The first time this happened, I deleted the caches and reopened the project. IDEA displayed the same error message in the same class, but for a different method of it's superclass (also correctly implemented in the superclass).
I closed IDEA again and deleted the caches, but when I reopened it, IDEA had reverted to flagging the class incorrect for not implementing the original method.
I can build and run the project, no problem, but the incorrect error flag persists for the class.
Who can rid me of this turbulent error?