The name of the scale can be changed to anything but not the definition.
I also tried
scalelist edit and change it to a different definition.. say name tbd, definition 1:100 , but the fields for changing scale are locked, greyed out.
Also true for original 1:1 scale.
It is like Autocad understands that both are originals 1:1 scale.
...and the only thing that stands out is this single layout that has tbd scale locked.
That's it the thing.
I know it is in use.. but all has been purged..
Inluded non-purgable list using SPurge.
Even if I delete all layouts.. it stills stuck there.
..but no worries.. I have built two new templates from ground.. and replaced these DWTs.
But it bugs me that this is still stuck there and I couldn't find how/why.
I will send a case to Autodesk and the file to see what I missed.. I will report back if it is something different than the scale being in use by an object that I can not find.