Switching away from the app and coming back re-starts syncing from some thousands of blocks later than the block number where sync got stuck. For example, I got stuck at block 8506 and after coming back to the app sync restarted at block 10350+.
So I got stuck 4 times during the initial sync, e.g. at 3k, 8k, 11980 and 13532. It re-started sync from 12100 or so when it got stuck at 11k and just displayed total balance the last time.
Switching away from the app and coming back re-starts syncing from some thousands of blocks later than the block number where sync got stuck. For example, I got stuck at block 8506 and after coming back to the app sync restarted at block 10350+.