iControl SOAP: Cannot delete UCS file on 12.1.1 HF1

The inability to delete a UCS file is the current hurdle, but I've found that I can't do much of anything with the ConfigSync interface, including saving a UCS or DLing one, for that matter. Pertinent Details:

 

Problem Version: 12.1.1 HF1

 

Auth methods used/attempted: TACACS and local Admin account - Doesn't work with either

 

Versions known to work b/c of testing: 11.2.x, 11.4.x, 11.5.x, 11.6.x

 

Any ideas? Is there a quirk that I missed in the v12 SOAP API or something?

 

My sincere thanks in advance.