You might post the content of “dmesg --follow” which occurs during unplug and replug.
FYI, for hot plug to work correctly the monitor EDID must work, and the EDID must be within one of the predefined values of the driver. You see if this file is empty, or if it has hex data (it should have hex data if EDID is good):
cat `find /sys -name edid`
Once you know that EDID exists before and after the unplug/replug you can narrow down as to what the driver thinks of that EDID via adding this to ‘Section “Device”’:
…then reboot, and check the content of “/var/log/Xorg.0.log”. The driver will explicitly tell you what it thinks of every EDID mode and what it has chosen or rejected. The log after unplug/replug would also give some valuable information, but you’d want to post just a simple log from after a normal reboot first.