I have looked at this and I don’t have a clue. Any idea I have for why this would happen falls apart due to the fact that getting a field from a post works but getting a field from options does not work. If this was something in ACF neither should be working.
The only thing I can come up with is that there is some type of filter being applied during the call in ACF to the WP function get_option(). The first thing I would do is search the code on the site (all plugins and theme) to see of any of the filters applied by the WP function are used.
It could be something in ACF that I am missing. You might want to contact the developers or open a ticket on your account.
