"missing plug-in" entries in publish services

Hello,

My list of publish services showing several entries named like "(missing plug-in) : <collection name>"; I want to delete them before they cause any trouble, but I cannot find how to do that.

Right clicking on these entries and choosing "Delete" shows an error message saying "Can’t delete the published collection(s). An internal error has occurred: ?:0: attempt to index field 'publishSettings' (a nil value)". Opening them in the publishing manager shows the empty Settings page with the "not saved" as the service name. Pressing "Remove" there gives the same error as before. Resetting settings did not help. Nothing suspicious in the Plug-in manager - all plugins I have show green - installed and running. Please help.

I am using LR Classic Release 12.1 on a 64-bit Windows 10 Home.