You need to quiz the Inspector more about the situation. If I can figure him out right, he's not going to tell you it's a show stopper, or not. HOPEFULLY, he'll tell you if the 'problem' is ongoing or an 'old problem'.
RE: What the current Homeowners say, take it w/a grain of salt. Go w/what your Inspector is telling you. From here, it's hard to say if there's a problem, and if your 'solution' is one that will work. Structurally sound is a subjective description. Again, press your Inspector. Oh, do consider a 2nd opinion (i.e., a 2nd Inspection by a DIFFERENT inspector.) Hopefully, you aren't using an Inspector that came recommended by the Seller's Realtor. You want one that's working in YOUR interests; not someone else's.
As I see it, it's only a few 100 $$$s now, or 100s of 1000s of dollars later (in the mortgage) AND you have to fix a problem!