Inky Impression garbled display

I have a problem with the Inky Impression on the RPi 0W - ~50% of the time Inky displays images correctly, but 1/2 of refreshes and I have errors “in transmission” [no feedback from python, just what we see]. Unfortunately I’m allowed to post only one small picture, but we can spot on the lower part of the picture some random white/black dots and then correct pixels but in shifted position. These dots always precede the shift (so they are signs of signal errors I think)

Do you have any idea what is a reason for this? Any way to fix it?