Devices lost Internet connection after upgrading

Hello, I updated UniFi OS to 4.0.20 on UCG-Ultra and Network application to 8.5.6 last night, since then my home network becomes very unstable, many devices in different VLANs lost Internet connection for unknown reason. Before the upgrade everything worked smoothly and I didn’t make any change to security rules recently. The strange part is some devices can make Internet connection but not all the time - and not all internet sites. For example my son’s iPhone lost connection, then I restarted UCG-Ultra, the connection was back for a while then stops working after 10 minutes. He’s iPhone is in a different VLAN (via virtual network override), if I move him to the main VLAN everything works again. I tried to find any difference between his VLAN and main VLAN, the only thing is content filter. I have disabled it now but problem still exists. I also tried to assigned DNS server 8.8.8.8 on his phone manually, didn’t help. There are also many issues with wired devices in my house - the music streamer not able to connect to Tidal and Internet radio is down either. My Tapo camera serves RTSP stream only to LAN and device doens’t seem to connect to Internet - but after some hours it managed to connect to Internet. All sorts of strange things, and I have tried to restart every single component without luck. Anyone has seen similar issues? And what would be possible to rollback the changes? 🙏 thanks!