M96 big pen eraser not working (big pen option checked)

Hello I have an Onyx M96 universe and I finally manage to upgrade the firmware thanks to that thread https://www.mobileread.com/forums/sh...d.php?t=255435 ( deleting the adb driver in windows device manager as pointed in https://www.mobileread.com/forums/sh...=255435&page=3 and the japanese link, was crucial to have the device recognized by adb)

the Problem I have now is that the big pen eraser is not working actually it writes instead of erasing... (indeed it was not working before because of the native firmware)

I tried to uncheck the big ben option reboot check the big pen option and reboot as advised in some thread here but this did not changed anything. I tried various firmware from 2014 up to last 2017 version but still have the same problem

The big pen itself is ok as I got it with an onyx Max and it is ok with this one

Thanks in advance for your help