Replying to the list, since a direct message to me excludes all the other people on the list who might be interested in the conversation.

Here I will try to describe specific steps which will lead us to the error 404 screen;

1- First we search for records with multiple items (books or serials, does not matter)

2- We open this record we found with multiple items for editing

3- We chose "Edit items in batch" option from the "Edit" menu

4- We make corrections on the fields under the "Edit item" (For example we change the collection code as "fiction")

5- We save this using "Save button" at the bottom, after we are done.

6- Just after we save, there will be a button named "Done" available just under the page, and when we click on "Done" we encounter the Error screen.

I have just tested this in master and I get the same results. I have filed a bug report: http://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=11475 -- Owen -- Web Developer Athens County Public Libraries http://www.myacpl.org