reassigning multiple bugs in bugzilla

[Gianluca Sforna]

Once I got the ownership of mantis, I search for all its open issues
on bugzilla, then I tried to reassign them to myself.
The problem was I could select all of them, but trying to apply the
modification (owner change) resulted in a error,something like: it
does not seem you made any modification.

Just to be sure it was not some random permission problem, I tried
with just one and that worked.

Anyone ever tried this kind of operation?