Just ran into similar, am using WebUI 3. Edited /axes/y/motor1/pulloff_mm from 4.000 to 6.
Reason for adjustment is that Min endstop arm snuck past adjustment bolt head and got bent enough to create ~2mm difference between when endstop arms trigger switch on Min and Max side.
Clicked save, click dashboard. Home Y axis, expected/actual pull off happens. But then…
Power down, wait for power supply green light to fade to black, power up. Click “connect again” in browser. Navigate to settings, fluidNc features.
Expected to see 6mm, but actually see old 4mm value. So, edit wasn’t persisted across reboot.
Will workaround by manually editing config file and uploading via fluidNc web uploader tool.