Elite Direto (Mk1) leg mounting bolt - loose nut?

Just moved house, and annoyingly to get the trainer in the box for the move, you have to unbolt the legs (it was a big stretch to get a $900 trainer for me in 2017, but I really wish I’d gone to a Neo or Kickr. But I digress). When I went to reassemble the legs, I found that the nut that one of the bolts goes into, was loose, and therefore I cannot tighten the bolt.

The base of the trainer has some sheet metal and a casting. My guess is that they put a nut into the casting from the top, rather than tap a thread into the casting.

I’ve started to google, but cannot find anything yet. Is this a common issue? And do I really have to disassemble the trainer to get to the nut and restrain it to tighten the legs?