Pyramid Autoharp String Set 36Ball End

I bought these strings for an Oscar Schmidt OS110 21FNE (which Thomann also sell) and actually had it done by a luthier, but he was only able to change half the strings.
Even though they are ball-end strings, they do NOT fit because the holes of the instrument are too small!
I would not say that I lost 76€, as I was able to change HALF of them, but it's still a big disappointment, especially as Thomann do not indicate that this is the case (Thomann or the makers, whichever of the two is responsible for informing the customers). All Thomann could tell me is that "the maker is not able to produce strings for this instrument"...