I have a desktop PC running Windows 11 with newest updates and drivers for the GPU (RX 6800XT) and chipset (AM4). After I lock my PC with WIN + L it takes around a minute for the main and secondary display to go to sleep. After a minute my secondary monitor turns on, stays black, the Windows device input sound comes from speakers and it goes back to sleep again. Then again a minute later this cycle continues.
Besides updates I have tried to change the displayport cable and refresh rate of the monitor to no avail.