I had an upload issue yesterday at a football match yesterday and it was very frustrating. Images, including a goal celebration, would not upload. In fact, it took nearly 50 mins to get an image out! I tried rebooting my 4G wifi device numerous times and tried my phone's hotspot. Nothing would work so I gave up trying.
I then shot a few hundred shots and, during a break in the action, ingested one of my cards. At that point, my images started sending. Everyone sent. I'm sure these are not connected but it does seem a coincidence?
PM5 Version 5.0, build 19749 (20d085a) on 2015 MBP 10.14.6