Yeah different play styles can have vastly different experiences. That's why we have playtesting :)
I understand that you made a conscious dissension with holding only one tape and this is completely fine. Can't make a stressful game relaxing just because some people want to have an RPG pocket.
Duno about the storage room. Abandoning the shop doesn't sit right with me. Perhaps making a two phase game could be a better idea.
In one you stand behind the counter take returns and sell new tapes with customers asking if you have a certain tape in the back.
In the other you're having to stock the shelves as quickly as you can.
Oh and what I also noticed, maybe give the cassettes some colors or other identifying mark to associate them to a particular part of the store?