Has anyone experienced Unifi/AP moving itself off the channel you manually specify?

I'm aware I'm using DFS, no radar alerts come up on the "alerts" panel. I can force another AP to use that channel and it holds just fine. But this Nano HD just doesn't like holding any channels. Including nonDFS.

I try to use these channels as I tend to use 80mhz channels to obtain 500mbps on any access point as I have gigabit internet access and want to free up channels for others to use around me.

I've had it for 2 years now, I have factory reset it and re-adpoted via Unifi.

Only thing that has changed is brining in a UDM-Pro and yes, auto optimize in the general settings is unticked. Used Unifi for about 5 years now and never had this until recently.
UDM 1.8.3-4 | Unifi 6.0.37