Okay this is a strange one. 1. Create a new HOLD notice template for a branch (not for all libraries) 2. Delete that new HOLD notice you created 3. Recreate the HOLD notice template for that branch 4. The HOLD notice for all libraries disappears and in the database the message_transports.branchcode field for HOLD now has the branchcode before it was blank. This causes issues with sending of HOLD notices.
I cold not reproduce this behaviour on Koha version 3.15.00.030 However, I could not create a HOLD message with Koha module set to "reserves", the drop down shows only Catalog, Circulation, Claim Acquisition, Claim serial issue, Holds, Members, Serials (routing list), Suggestion. The only way to have HOLD with module "reserves" was by making a copy from (All libraries).
Can't test this as it's currently not possible to add mulitple letters with the same code :(
This should be fixed.
Retested, it is fixed.