The problem accour in the final step of PSBT, when the seedsigner generates the qr containing the signed txo. OBW isnt able to recognize the qr and shows an error. It shows a load screen when scanning qr that end at 99% with the fatal error.
The seesigner signin seems to work (no error reported, no unexpected behaviour and the final qr is correctly generated).
The same issue is present in SBW.