Copying a button from a page to the footer (or vice versa) does not create a new id nor a new class for the copied one when inserted (took me some time to sort out why changes for the copied button does not have an effect at the front-end, only within editor then)
This is intended behaviour as it is considered that block IDs should be unique on the page, but not globally. The same applies to classes in this specific situation.
Basically, if Cwicly doesn’t find a similar ID/class on the page, then it will automatically rename it.
We used to rename them before they were copied to clipboard (which was much easier for us). But the nativecopy/paste function in Gutenberg is not hook-able, which means that the renaming process has to be done after the block has been inserted.