I have found a bug in the ACF Repeater Field when duplicating layouts.
When duplicating a layout within a repeater field, for some reason only 16 subfields in that copied layout are saved. The other subfields disappear completely upon saving.
Editing the duplicated subfields before saving does not resolve the issue.
If this is a known issue I apologize.
Thank you for your hard work. ACF is certainly the standard for WordPress plugins.