I get an other mail, that after the update, I have to do a full firmware update. Maybe it could help? I'll try it. Unfortunately just after work, becouse that's my wife's reader, so I can do experiments with it at home.

I searched for the version number of the EPD waveform on the device, but before the update I had the same version number. And so the update's number is the same: BL_P038_00_23
So maybe a firmware update after the waveform update could help. Who knows....