@nowosad
Do you have those values as a list IN the dialog box used to establish the dropdown? I'd actually recommend doing it differently, for a couple of reasons. The most important are visibility and maintainability. In general, unless there's a compelling reason to keep that kind of thing behind the scenes (and even then you can use protected or hidden sheets) I think it's good to have tables for data validation and other purposes (e.g., various forms of table lookup) on one sheet in the workbook that is dedicated to that purpose. It helps with documentation, with maintenance, etc. If you ever get to the place where dynamic and changing drop downs come in handy, they definitely are in a backup sheet. See the cascading data validation example attached.
I don't know if that could be the cause of your difficulties. That slash in the middle of some of them could trip up some, I suppose, though why it would be selective I can't imagine.
