When performing a batch patron modification to a set of borrowers, the editing field for library does not modify the patrons home branch after saving. This doesn't work when modifying with a patron list, a file, or a list cardnumbers. You do not get an error that the modification didn't work. However, the field remains unchanged.
Retested on current master, it appears the bug has been fixed since!
*** This bug has been marked as a duplicate of bug 19073 ***