How to fix broken camping chair

[Rololux]

I know there are loads of threads on broken camping chairs, but I could not find an answer to my specific question. On both my chairs the left hand side bolts at the bottom of the upright section have both come loose. I managed to retighten one of them, but the other does not seem to have a captive nut or whatever indies the chair tube. My question is, exactly how is this supposed to work?

I’ve got a replacement parts set, but before I take the chair apart, and prize off the plastic end caps to have a look inside, I’d like to know what to expect. Is there a captive nut, which may have come loose, or is there a ‘welded’ threaded part which may have broken off? If it is the former, I’m prepared to take on the repair myself, but if the latter, I will probably try a warrantee claim (I have the 5 year VW warrantee).

Thanks for any insight - a full diagram of the chair would be even better!