I suspect it's user error. Check your input in Client Info Resident Status and Screen 55 Part Year Info.

I get D-40.

Client information screen shows resident state as of 12/31 DC.

Full year resident - blank

Multi state return

Screen Part Year/Non Res information:

D. C. Part year resident from  07/01/2020

Will go to the tech help for this.

I think DC Resident from 71/2020 to 12/31/2020.