Attach Repeater to Container within Lightbox?

I am using lightboxes to display a view/edit/update screen to the user and then passing this data back to my page and other functions. This works fine.

In my lightbox, I have a container box (which will be collapsing/expanding), and a repeater.
Normally I would just drag the repeater to attach it to the container box, however this is not working!

Is this inability to attach the repeater a feature of lightboxes or am I just missing something?

It should work the same. If it doesn’t, you should contact Wix Support:
https://support.wix.com/en/article/contacting-wix-by-phone-3491545

Thanks for the confirmation @J. D. Interestingly, I since found that it works if I create a new repeater from the menu, but not if I copy an existing one from another page in my site (to maintain formatting.)