The same issue from this topic was also happening on all three of my Manjaro PCs, so I had been holding off on updates after the [Stable Update] 2026-05-27 release.
Then [Stable Update] 2026-06-26 came out, and I thought maybe this problem had been fixed, so I tried updating.
It still wasn’t fixed.
After that, I started investigating the cause and found the culprit.
The culprit is libxfce4windowing 4.20.6-1.
Until it gets fixed, I’ll keep using libxfce4windowing 4.20.5-3.
With libxfce4windowing 4.20.5-3, this problem does not occur, whether I reboot or turn off the display.
It looks like XFCE is already aware of this issue, so it should be fixed soon (probably).
It seems to occur with combinations of certain displays and HDMI or DisplayPort.
In my case, it occurs with the combination of Dell AW2725DF, AW2521H and HDMI or DisplayPort,
This problem does not occur with ASUS or Mitsubishi displays.