Are these 8K AVR's?
If so... the issue is much like what we saw when when 4k/HDR was introduced, it is the inability to quickly resolve which format to use.
Often a Hot Plug Reset will fix this, (easy test) turn system on with HDMI cable detached, then plug in cable, if system now works correctly instal our AIO2 between the AVR and the display (IMPORTANT NOTE: AIO2 must be triggered by contact closure, if you do not have a control system on the job use our CS-IRKITCCUS).

[Link: metrahometheater.com]

[Link: metrahometheater.com]