Try making a copy company and doing your adjustment in the copy. 

Full disclosure, I'm not really up on what those fields hold. Not much of a W/O guy.

That being said, I just edited those 3 fields in my XYZ Company and didn't have any trouble. I'm in 2021 Standard, though, with PU 6.

I can edit the fields, but if WO1, field Total Completed is zero and I need to adjust it to more than a single digit, it doesn't work.  For example.  I show that 321 units were ordered (field 4) and Qty planned (field 6) was 321 and then try to change field 9 (Qty Complete) to 321 when the field says '0', if I enter '321' it will only change it to '3'.  It is very strange.