Hi, this issue concerns ACF Pro v. 5.7.0.
In our website we’re using a select-field within a flexible content field, which has the values set via the plugin like this:
33 : 33%
50 : 50%
66 : 66%
100 : 100%
When editing the post the selectlist shows no values to select (completely empty), or in some cases only the first option.
Reverting back to version 5.6.10 resolved this. Please let me know should you need any more information.