Your chart plays as written time after time for me (iPad mini) AABC x30
I am unable to replicate the jump-back to the start you describe from just before the first ending on song-repeats after the first play through the form.
It's a mystery.
Have you experimented with:
other songs using similar player settings?
same song different player settings?
Try a double-press of the home button (or a multi-finger up-swipe) to see what other apps are open...
Close (single finger up-drag) app's you're not using.
Does the issue persist?
The usual suggested remedy for odd digital device behavior is complete power-off/re-start.
Does that "fix" it?
I edited your chart to conform to iRp lay-out conventions. (added a missing bar-line at the beginning of the 2nd ending. Its absence didn't appear to be causing any problem)