If i was the lens, then redoing the test without stand development should reveal that problem clearly.
If you shoot with another camera and use the same stand method, then if you have the problem it is bromide (or chemical) drag. And yes, it can appear quite sharp, especially with larger formats.
I am not against stand ether, but it is, as I said, an art. You don't just walk into it and do it the first time. You have to fine tune with different methods until you get things just right.