I installed a few weeks ago B&R 9.5 U4a and we have exact the same situation.
One of the differences, we have a HP StoreEver MSL2024 with LTO5 drives and barcode reader ... (these info just to show that this happens with automatic too)
However: every single Tape we used had wrong slot numbers as "original slot" and we found out with the fresh tapes we get away with erasing them (short is enough) and the the slot was working.
and now to some "funny" stuff:
After some tape rotation, we put in some tapes we used before and we got the same problem again: wrong slot numbers at the eject procedure.
After looking into the db from Veeam I found in dbo.Tape.tape_mediums that there is the wrong slot set at "original_slot" - even the right one is at "location_address" right next to it.
I can try hundreds of things but "original_slot" won't change to the number it was scanned after switching the tapes.
When this happens, than it is possible to load the tape, but not to eject it afterwards!
Now what I found out (just to help others with the same problem - the library is not 5 walking minutes away ...) load the tapes, erase them and then use HP Tape Tools with the "eject utility". After switching back to online the tape library need to scan itself and then the tape is in the right slot! Also in the veeam db!
Sadly, only the tape which was "emergency ejected"
So, my conclusion to this: Maybe it would be easy for veeam, if there would be a "rescan slots" button anywhere or a powershell command for scanning all slots with the tapes and writing the found slots into the "original:slot"
It may a little stupid program which can do that after swapping tapes and there wouldn't be any big problem for anyone...
For sure, anyone else could do it too, but it would be nice, if the code-writers of Veeam would do this for their created database.
After a long search on the internet I can tell you: I'm not alone with this problem and always telling people "mage a call" won't help on the long way!