Working on custom plugin, based on https://github.com/Freso/picard-acousticbrainz/blob/master/acousticbrainz.py
(error happens even with this original code...)

in this case, if you request info for a MBID that doesn't have acousticbrainz info from the website, it yield a 404 on the website:

example error from Picard log:
E: 21:20:29 Network request error for http://acousticbrainz.org/feaaf9a9-d6a7-4f07-9485-1df9faa002f8/high-level: Error downloading http://acousticbrainz.org/feaaf9a9-d6a7-4f07-9485-1df9faa002f8/high-level - server replied: NOT FOUND (QT code 203, HTTP code 404)

While the plugin continues running, the counter of number of requests doesn't reduce, meaning that any/all 404 continue to be 'pending', and thus yield a false number at the green arrow.

If the original code isn't doing something correctly, please help with the correct way to clear this, but my reading of the code and debugging says that
webservice.py _process_reply( is where the error comes from, but once it occurs, it should be clearing the request anyway.