Nothing odd about last minute bids. I always do it. Decide what it’s worth to me, bid that, if I didn’t get at that price I didn’t want it. Bid earlier and you risk losing it to somebody who wasn’t going to bid more than you but can’t bear the thought of losing.
Does the buyer have recent feedback? If so, I’d just give them time. Last time I sold anything, eBay rules were that it had to be Paypal, in which case it’s a bit odd not to pay as soon as you win – or is that what you mean about last minute bid, ie, must have been online to bid so why didn’t they pay then?