KUAL stopt working after downgrade

I successfully applied the jailbreak om on my KOA3.

I got MRPI and KUAL installed, blocked de OTA with renameotabin en downgraded to SW version 5.12.5

I still see the KUAL button. But it won't start. It gives me an application error.
I tried reinstalling KUAL but nothing happend. The install fails silently.

I'm obviously missing somthing...but what?