There will be no update for MFS:
Currently in MFS I see no need for an advanced flightplanner. There is no advanced aircraft which could make use of it.
If you want one anyway, I suggest to use Simbrief:
Same question to you. Are you 100% sure that you used the correct v4 or v5 installer for the A320/A321.
Can you check the asc.cfg file from the previously mentioned location and if you have "UsePrepar3Dv5=0" set accordingly. 0 for P3Dv4 and 1 for P3Dv5
I am not sure right now other than using the wrong installer what could go wrong with the update process because I am simply unable to recreate this issue myself when downloading the latest installer for v4 and v5 and then applying the update there.
All of our aircraft currently uses the 8.33 kHz spacing where the frequencies are read directly from sim via simconnect and then recalculated according to user input and written back directly into sim. So the only change was to change the radios from 25 kHz spacing into 8.33 kHz spacing system.
We'll check this on our side as well to compare between different internal versions to see if we can find something that broke this feature.