Question about Pioneer VSX-LX305

The inputs are set to "4K Enhanced" as standard (4K/60Hz, 4K/60Hz HDR). A Premium High Speed 18 Gbps HDMI cable is required for this resolution.
You can also set the setting to "4K Standard" (4K/30Hz). Then you need a high-speed HDMI cable that supports 10.2 Gbps. It depends on what the TV supports.
I would replace the cable. If the problem persists, set the streaming HDMI output to "4K standard" in the receiver's Home menu.

If you can, change the cable.I had this problem on a Denon and bought the Pionner.Same problem with Sunrise and the black screen (but less often) changing the cable solved the problem. If you continue to have this problem, change the input of the amplifier to 4K Standard for the box AND for the TV. Once you've found the problematic cable, put the best cable for the TV back on and change the one from the box to 4K Enhanced.

My behaviour is very similar, maybe not every 5 minutes but from time to time, I haven't found a solution yet, the firmware update didn't change anything.

Pretty much a broken cable

I wouldn't know which setting could cause such behaviour. Sounds like a defect to me. Have you tried a different input?
But it could also be a bad HDMI cable.