I would be very surprised if this has anything to do with the MDM agent.
I wonder if when they remove the MDM agent they reboot and the reboot is resolving it.
The second thing I wonder if it is just a time issue, and by spending extra time removing the MDM they are masking the issue - and it is the elapsed time that has sorted the issue rather than the software removal.
Presently I am spending time at an organisation that has a singularly awful WiFi. It frequently "appears" to hand out IPv6 IP addresses to client devices expecting IPv4 addresses. The result is that there is no access to the internet.
My solution has been to stand under the closest AP with a mobile phone, restart the phone and then make a functioning connection to the AP. Having done this, I go back to where I am using the laptop and tether the phone to it.