Merger sites - bad files list

I have been debugging a problem with (temporary) lost merger site permission (see closed issue Question: Not a merger site! #944). I can see that the error occurs (lost merger permission) for fileGet request to a file on bad files list. Adding a list of bad files in my code solved the problem.

Any way to get a list of bad files in ZeroFrame API for merger sites so I can avoid downloading files on bad list? Or alternative a better fileGet error handling in ZeroFrame API. Empty fileGet response for bad files would be OK for me.

The issue names the ZeroFrame API and its fileGet entry point but no files or tests. Start by locating fileGet handling and the merger-site permission path, then determine whether a bad-file list or an empty response is the intended behavior. Done means the selected behavior is implemented and covered by relevant tests.

Written by the indexing model from the issue text.