To recreate: 1. Set system preference, itemcallnumber, to 082ab or something similar to pull the call number from the bib record into the item holding. 2. Create item and remove the call number. 3. See that the callnumber has been removed in the item. 4. Edit this same item and see that the call number is back (pulled again from the marc record following the itemcallnumber sys pref). This is an issue if a library does not want a callnumber in some records but does for others.
I'm seeing this on the 20.11.09 release. I'm also seeing situations where the callnumber has not been deleted from the item record, but it not showing on the holdings table and it is showing in the o - Full call number field when the item is edited. Then, when the item is saved, the callnumber starts to appear on the holdings table.
Confirmed this on current master. I think this could not only come as a surprise, but lead to unwanted changes in people's data. So moving from enh to a bug. But as always... maybe someone is relying on just this behavior? Would be good to get some more opinions.