The sync in Premiere Clip is incredibly slow, and if I exit the app, it stops the syncing and starts over at 0%. This is honestly horrible. Any way to fix it?
The files need to sync to the cloud in order for you to send you project to Premiere. However, you should be able to background Clip while the sync is taking. Just make sure it's put in the background and not closed. I just ran a few test and it's working for me.
It is possible if your device is low on memory, Apple (iOS) will intentionally kill the background processes to conserve memory for apps that are in the foreground.