I just had this same issue. No matter which ACF field I created, nothing got saved. I tried opening the default WordPress Custom Fields from Screen Options and those worked ok.
I had pretty much just ACF, ACF repeater and WPML installed on a WP. I ended up clearing the whole database and recreating the few pages I had, which resolved the issue. If you like, I can send you the non-working db-dump.
I have the same versions of wp and acf as PapaBearNZ.
