It happen something like that to me. Updating saves the data that was read fine from the DB to the post editor, but is not found in the front end until re-saved.
The problem was my fields being created by code and there was a duplicate field key (duplicated on purpose – I assumed the source of the meta-custom field in the DB would be shared for both ACF fields).
The duplicate field key doesn’t have to be THE ONE of the problem. Just by having one duplicate field key in the same group, it can ruin other fields (most probably the ones created later, not the ones before, since the hole in the array generated by one element using an existing key instead of another one affects the NEXT items in the array, not matching the original index… or so).
Good luck.
