HP U28 4K HDR Monitors frequently don't turn on when system wakes from sleep

[Ollonii]

I have two Radeon Pro W6600s in a Dell T7920 Workstation. Each W6600 has two HP U28 4k HDR monitors attached via DisplayPort. Most of the time, everything works very well but occasionally (about 25% of the time), when the system wakes from sleep, one of the four monitors doesn't wake and remains undetected by the system. The only way to get the "missing" monitor back is to remove and restore power to the monitor (shutting it off is not sufficient). The monitor that doesn't wake in these cases varies, seemingly randomly, and might be on either of the cards. I've also had one on each card refuse to wake. I've also tried two NVidia RTX 2080 Super cards with the same results. There doesn't seem to be much information on these monitors around, but I wonder if there's a firmware update that adjusts the sync sensitivity when they're in sleep mode?

For reference, the O/S is Windows 11 Enterprise Build 22000.493 and I've tried both sets of Radeon Pro drivers (Radeon™ Pro Software for Enterprise 21.Q4 and Adrenalin 22.2.2). The system has two Intel 4210 CPUs and 192 GB memory and both video cards are on CPU1. The monitors (and cables) are certified for DP 1.2 whereas the W6600 is DP1.4 (which shouldn't matter). The W6600s are using the latest VBIOS (received from AMD).

Has anyone else experienced this behavior? Results can be unpredictable when a monitor shuts off during a design session so this is more than inconvenient. Thanks for any help.