Same here - My UDM Pro is over 90 days uptime, and that last reboot was only because I did an upgrade. I have heard of some people having problems, but mine has been flawless so far.
I've ordered a UPS and I guess I'll see if that's the issue.
I use a lot of fans in my house to circulate air, and when someone uses the microwave, half of the fans slow down, and half speed up significantly. no idea how half could speed up, but they do. so, something is up with something, somewhere.