Comment 3 for bug 166245

Ah, pasting _back_ explains it. This in all probability is a
dupe of

https://sourceforge.net/tracker/index.php?func=detail&aid=1024331&group_id=93438&atid=604306

Since the changed gradient still uses the same ID, on
pasting back it reverts to the old version which you had in
the old document. So, if you really need to copy/paste back
and forth, a workaround is to use XML editor to change the
id of the gradient and the reference to it from the object
style before copying. Yeah, it's very inconvenient, but it
should work.