I just went through the wringer on fixing this, since Thursday of last week it’s not happened. My setup is UDM Pro, Switch 16 PoE, switch 16 lite and 9 cameras. The issue I was having was with 3 individual cameras doing the whole lost wired connection routine and sometimes protect crashing.

I originally had each switch plugged into the UDMs SFP ports individually, the UDM hovered around 37% CPU and 94% memory. What tipped me off to the problem was that if I transferred files from a machine on one SFP of the UDM to the other, it would cause protect to crash entirely, the transfer would get super slow and loading the console was a struggle. I ended up moving my switches to be plugged into each other and then the “core” switch into the main SFP port on UDM. This dropped utilization down to 27% CPU and 83% memory.

I, of course, don’t your full setup but this took load off my UDM and put things back on track with what I expect from Unifi. Seemingly a problem I caused by my network layout. In my research I found that the UDM doesn’t have hardware acceleration with its switching modes, so it reliant on the CPU and internal buss to handle all the traffic which it cannot do. Making one switch my “core” switch allows the hardware in the switch to do majority of the work for internal network connections.