MinimServer fails to start: 'Incorrect tag name' new error

[DavidHB]

As of this morning, with nothing changed by me, both MinimServer installations on both my QNAP NASs failed to start. The log gives the following:

Current time is Tue Oct 31 12:36:48 GMT 2023 in time zone Europe/London
MinimServer: incorrect tag name 'ComposerSort' in property 'tagFormat'

The tagFormat property which contains this error is

ComposerSort.displayFormat={$composer},Title.displayFormat={$composer$title^^^: }

Removing the whole ComposerSort reference from the property allows MinimServer to start. However, I am confused as to why the error has suddenly arisen. As the MinimServer installations are, as near as possible, mirror images of each other, I have left one installation uncorrected, so that I can apply any fixes which may be advisable, and then copy them to the running instance of MinimServer

For information, the other tags in my installations which reference ComposerSort are indexTags

ClassicalGenre=Classical:Classical library, Genre, ComposerSort:Composer, Composition, Artist, AlbumArtist, All Artists, Conductor, Orchestra, Soloist,Date, *RecentAdded, *RecentPlayed, #AudioData, #AudioFormat

and tagOptions

Album.sortTags={Genre,ComposerSort,Album},all.ignore.sort={The,A,An,Der,Die,Das,​Ein,Eine,Le,La,Les,Un,Une,Il,El}

In tagOptions in the MinimServer instance which is now running, I changed 'ComposerSort' to 'Composer'.

I'd be grateful for advice on how to deal permanently with this error, which, as I said, has me stumped, because it seems to have arisen spontaneously.

David