Ghosting with partial refreshes with 1.54inch V2 e-Paper Module

[W11T]

Everything worked well until i had to switch to 64bit Debian Bookworm and hence to use the latest versions epd1in54_V2.py V1.1 (2022-08-10) and epdconfig.py V1.2 (2022-10-29).
As advised in https://www.waveshare.com/wiki/1.54inch_e-Paper_Module_Manual#accordion19 i use code like

            epd.init(isPartial=True) 
            epd.displayPart(epd.getbuffer(disp_image))
            epd.sleep()

But using this recent drivers this code gives a weak image in the updated part an leaves heavy ghost images.