See: https://support.plex.tv/articles/credits-detection/
Nothing
Credits Detection has a bug, that might affect limited platforms. We are currently investigating this
V1.31.0 of Plex Media Server
Simply disable it for now, and you should be fine
Not yet, but it’s a priority for us
Yes. If you setup a PlexData share, you can then delete using QNAP’s filestation
See: Qnap faq.....read me first! - #5 by ChuckPa