I was getting those messages too, weeks ago. I believe it is the transaction/search timing out. In my case I was doing searches for a route (YYZ/BKK) that has many flight options and it would time out at about 45 seconds.

Due to the storms and flight cancellation recently, yes there is probably some extra load on the system causing the 45 second time out to be reached.

I happily informed United Support (many times) but no change. This is just a poorly designed, inefficient system that they don't seem to care about.