Boy do I feel for that candidate. As a manager, while this is not the kind of question I'd ever ask, if I saw a candidate work through a problem like this I'd take it as a strong signal for a possible hire. Ghosting is a dick move period, but especially after a performance like that. I would like a follow-up discussion probing how open/accepting they'd be to skilling-up in their weaker areas, how they go about asking for help, try to suss out if they're prone to getting stuck in "ruts". But if I didn't see any red flags my vote would've been yes.