There is a fork of the plugin that fix the issue of adding n number of instances in a flexible field :
https://github.com/mvpdesign/acf-reusable-field-group
That actually seems to be a fork of a different plugin than the one mentioned above (created by @beneverard). I haven’t tried it before but it looks interesting thank you, I will try it out on my next project (that requires it) and report back.
This is still a feature I desire greatly from ACF and would love to see it as part of the core functionality (or happy to pay for a premium add-on).
