I’m having this (not so big) problem. It really isn’t big, just annoying: every time I try to exit a page or post after saving it, WP asks me if I’m sure because there were changes. No matter how many times I save the page or post, the message persists. However, if I deactivate ACF PRO the message disappears.
I tried this on another page using a different set of field groups and the problem is not there. The only difference between both groups is that the one with problems use the Flexible Content field. I assume the problem is there, but not sure. Anyways, it’s worth mentioning.
Anyways: is there a solution for this issue? I’m using the last version (and previous versions had the same problem)