I'm going slightly mad; Chime Pro2 and Unifi

Hello folks, After 3 days worth of troubleshooting and practically tried every single option 'the internet' has posted including a replacement Chime Pro gen2, I'm going slightly mad here. My setup is simple; Video Doorbell pro and Chime Pro 2nd gen both connected to the same access point for months without issues. Then, Unifi UDM decided to upgrade to 2.4.27 and since , Chime Pro cannot establish connection to internet. (red flashing LED) So yeah, simple , fault is at the UDM side and I agree but wait for it. I still have an older Chime (non Pro) which connects perfectly fine... Older chime sits next to Chime Pro using same access point , same physical location, same 2.4G wifi network , same password etc. Pro refuses to connect to internet. Pro does get an IP during initial install but then disconnects. ('there seems to be a problem with your internet connection") So far I've tried -rebooting UDM -removing and adding countless times through the app using different setting -creating open Wifi network dedicated to Ring on with 2.4G on a dedicated AP -changed DNS setting to both 1.1.1.1 and 8.8.8.8 -guest hotspot without credentials -setting up through app with Bluetooth and network turned off -checked every possible setting in UDM - that made sense to me -went through a support call and was kindly sent a new unit, still same result (can't beat Ring support) -updated firmware - added a wired RaspberryPi to act as an access point and Chime connects perfectly - connected to iPhone hotspot and Chime connects perfectly Adding and removing the older Chime (non Pro) works flawlessly every single time So main question is : what is the difference between Chime and Chime Pro, any additional ports I need to open as I've checked those as well to no avail. appreciate your wisdom