Elements in tabs won't stay inside them

Hello everyone! I hope somebody had this same issue and had solved it.

When forming a huge form using tabs areas, after I manage to get all the elemnts inside the tab container they belong and save or apply changes to the form, all elements go back outside the container tab...

This is kinda driving me crazy because there are a lot of fields.

I've tried to do this with the demo form and does not happen: all elements stay inside their container.

Why is this happening? I just want you to know and also, if I can solve this would be perfect because I don't want to re-do the entire form again... 😑

Thanks!!

S.

UPDATE: I've noticed that if I add-drag a brand new element into a tab container, it will stay there after saving the form, but if I add it outside the tab, save, then want to re-locate it inside the tab it won't stay...

May this be a bug? or, am I missing something?

Thanks again!

S.