The "slow UI" issue could happen when Headwind MDM app doesn't have a "Draw on top / draw overlay" permission but a disabled app keeps running.
To get the info about disabled apps, turn on the logging: https://qa.h-mdm.com/1573/
You will get multiple messages like "Blocked package by usage stats: .....". These apps must be enabled (here's how to).
In your case, most probable reason for the issue is that you didn't set Headwind MDM as a default launcher.
You can check the default launcher by clicking ... - Detailed Info in the device list.
Here's how to change the default launcher: https://qa.h-mdm.com/2211/