Repeatable groups with image files get deleted

I have a repeating group with an image upload and textfield caption. Everything works ok but when I have more than 10 image groups (e.g. 21 images with captions) and if at that point I delete the featured image then update the post, I lose 11 groups and always end up with only 10 groups. Im not sure if there is a pattern to the groups being deleted but it seems random. My client is also reporting the same problem and he says it also happens when he edits values in other metaboxes created by CMB within the same post or when he sorts the repeatable groups in the post.