Alternate tuning guitar TAB

One more time, this is a new effect of the misunderstanding, confusion of the "Open" string display in "String Data". This function has nothing to do with the word related to folk or electric guitar, for e.g. D open chord/ or Dropped D.

Excerpt of handbook: Mark unfretted string "open"

This feature is used to mark a (bass) course as unstopped (i.e. outside of the fingerboard and always sounding open): as on a Baroque lute or Theorbo etc. This means that only "0" (zero) or "a" is accepted as a fret mark: any other fret mark will be converted to 0/a.

So, here, that's what's happening: : fret 5 is rejected on this 6th string and, in this case, put on the string of the same name E /other octave
Uncheck this Open D (again, it's unuseful and source of mistakes) in String Data, and it returns to normal: dropD.mscz

See:
https://musescore.org/en/handbook/3/tablature#edit-string-data