When using the collection widget, with the mopaboostrap-collection.js you can end up with duplicate indexes which results in either errors when processing the form values, or data going missing.

Easy to reproduce:

1. Start with a collection of 3 items
2. Delete the first item
3. Add a new item

You will see that the second and newly created third item will have the same index of [2].

They only way to use the widget in it's current form is to add all the new items you need, and then delete the ones you don't just before saving