Update errors should not vanish
I tried to upgrade yesterday to 3.3, but after requesting download it said "preparing update" and shortly after that a notification came up with "cannot determine size of update". It took me multiple tries to actually see that as this message does not persist, so if you are not looking at the device exactly at the time this pops up you will never see it.
Also this message is completely unhelpful as it does not point to the actual reason. For me I got errors when trying "pkcon refresh" that said that repomd.xml could not be saved to /var/tmp/AP_0x{random}/repodata, which is unhelpful by itself, but a much better hint that it is a local problem instead of just a crowded server.