Do you have a TV or projector attached to your AVR?
If so, try disconnecting it from the AVR and see if that makes any difference to the NUC/AVR behaviour. It could be an HDMI handshaking issue across the complete chain, rather than a cable issue (although this is certainly a possibility).
If it is a handshaking issue across the complete chain, then this can be tackled, but it’s not cheap; see: