Yes that definitely looks odd. Does the pin 7 terminal protrude farther on the underside than the others? If it doesn't look like something that can be adjusted we can certainly send you a new tube socket and whatever you might need to replace that is connected to it.
On the bottom, the pins look fine, but they look misaligned. It's hard to describe, but when you look from the top at both 7-pin sockets, the orientation is identical (i.e. the angle of where the gap in the pins points is the same). When you look at the bottom of the chassis, the placement of the pins is slightly different between B & D sockets. I wonder if the moulding of the socket went wrong for the one in Socket B. I've ordered a set of new sockets from a local retailer for the sake of time and happened to go gold because that was the only option on the 7-pin sockets so I wanted them all to match.
I'll provide an update when I install the new sockets to confirm if the problem is resolved.
