There is something odd here. The raised moulding along the back of the Thornycroft should, I would have thought, form a continuous line around the three sides.
Two sides, yes. The short one, no. It misses by several mm.
At least it's another easy fix. Removed the raised lump with a pair of wire cutters (those ones meant to cut flush to the surface, very handy for this sort of job) and file. A quick polish with a bit of emery and the surface is clean. I'll re-instate the line with some plastic later. After I finish with the soldering iron.
Talking of which, the sharp eyed will notice that the corners have been filled with blobs of solder. It's a good filler as well as fixative.