Happened twice to me now: Duplicated a normal repeater field, with the intention to move it into a flexible content field which was residing in a different Field Group.
So, duplicated it, moved it, opened another tab with the other Field Group, and then moved it into the resp. flexible content field.
All the settings seemed to be ok. Is being displayed properly, nothing missing in the ACF Editor.
But when I tried to use the fields in the WP Post Editor, either the fields would not be displayed, or just as simple text fields.
So I thought: Might be an issue with the display option (block, row, table etc), so I changed that, and after hitting update .. suddenly the whole field was deleted.
Ie. flexible content “blocks”, but WITHOUT the fields that I before had moved there!
3 hours of work gone poof. Lots of fun. So I decided that apparently ACF doesnt like repeater fields in flexible content fields anymore. Ah well ..
On the next day, I tried it once again, with similar results. After duplication and moving them to a different field group, no matter if I dragged them into repeater or flexible content fields, their original functionality would be lost. First I thought it was an overlap of the variable names, but even when changing them after duplication but BEFORE moving them to the other field group, the functionality was still somehow lost (although being correctly displayed in the ACF Editor!).
The only thing that works now is to create the fields completely anew. Also, with no kind of auto-backup available (something like ACF revisions would be VERY helpful), similar to what happens when updating Posts and Pages, one has to constantly export data, else it might be lost again :-/
Things to note about the platform: This is a pristine WP 4.7.4 installation. Aside ACF there are no other plugins activated. Also, there are just about 15 pages around (plus the default dummy content WP sets up during the installation process).
WP: 4.7.4
ACF: 5.5.13 (Pro)
Environment: Ubuntu 14.04 LTS / 64-bit / PHP 7.0.5 / memory_limit 256M / max_input_var = 3000
