Hi,
Firstly, @Luke what has happened to your Bazinga avatar! you have always had that!
Secondly 😉
I have a few weeks ago installed the open subtitle plugin and it seems to be doing it's job but I am seeing these alerts every day and not sure what is happening? Also I notice particular episodes that are generating these messages have an awful lot of subtitles downloaded? the files that are mentioned in the alerts are still there in the cache/temp folder also