When closing - the display does not turn off (only just before closing)

Very strange thing started happening with my Macbook Pro 16'' 2019: when I close the display, shortly before closing it turns off, but when closed completely, it turns on again and keeps on all the time. When I slightly open it, it turns off, but when closing again, it turns on. Very weird - what is happening ? I did all the resets (PMC, PRam), still the same ...