I think this is about where you put the blame; on the lack of quality control. As I understand most instruments leaves the factory, merely assembled, not adjusted.
First thing I noticed was the large amount of sprouting material that stuck out of the slots in the nut. Ok that's sloppy but no biggie, however as I tried to remove the strings, they were almost impossible to yank from the slots, Like instead of filing the proper dimensions, the assembly guy had somehow forced the strings into place, lets just say that it wasn't tuneable.
2: only the knob for the bridge pickup, which turned with a weird resistance to it, had that notch so you know when it's middle centered, however the bridge pickup did not work at all. The other knobs turned smoothly but without that middle centered notch thou.
Of course the overall problem is the sloppy assembly and the non existent quality control in Epiphone far east factory. But as a retailer you should be aware of checking the products you sell too.