I completely understand your frustration. Get ready to experience a lot more of it. Very few of the vendors produce a 100% accurate, concours quality part.
I’m not trying to justify the short nut, I think it is pathetic that parts like this are produced and sold when the vendor knows damn well (or should know) that the parts don’t work as intended. As was stated early in this the thread, return the part to the vendor, hopefully they have a better part for you, or can refund your money and use the info to correct their defective parts.
However, I’ve been messing with 914s a long time and can tell you with certainty that having a part that can be made to work or modified to work is better than no part at all in many cases. Even with the multiple vendors that we have, there are still a lot of NLA parts.
If you are wanting to put together a concours level car, you’ll be much better served by trying to find OEM parts used on the WTB forum rather than buying new aftermarket.
Good luck with your build and sorry you’re having to deal with shady parts.