Okay I see what you are saying. I haven’t ever received a report like that so this is likely something unique to your installation.
When I have had some quirky behaviors from ACF fields in the past, I’ve sometimes been able to fix them by deleting and rebuilding the field group to start fresh. In those cases I don’t really know what was going on under the hood in ACF to cause the issue but fixing it was enough for me. So that is one thought you could try.
Another process you could go through is a bit of trial/error to see if any other code or plugin you have active on your site is causing a conflict. So you would disable everything that isn’t needed here to test this, see if the problem goes away. Then start adding things back slowly to identify the conflict ( if there is one ).
Sorry I don’t have any more specific advice to share with you, but you are the only report I have of a problem like this so I don’t have any background yet on what could be causing this. If any of the above helps you, or you figure out some other cause/solution for this, please write back here so that it can help others in the future.
Thanks,
Matt Keys