I have today made some changes to the way that APRS2SOTA attempts to ensure that a spotted callsign matches the format that users might expect to see for a spotted summit. That is it will add a regional prefix when it thinks one is required.
The original method of doing this was quite a complex set of individual checks in the code based on the assocation and required code changes each time something was noticed that was not as expected. The new method is effectively a lookup table (although that is still complex) and can be changed without changing the code itself and should make it more flexible and easier to update.
If you see any spots from APRS2SOTA that appear to have the wrong (or no callsign prefix when one might be expected) then please let me know the details of the spot (Date, Time, Summit and Callsign) and and what you think is wrong and I will try to correct this for future spots.