It could be something to do with a family issue. One spouse could be pressuring the other to sell or something.
I'd steer clear of it unless you are prepared to go through what could be a rollercoaster sales process, with disappointment at the end.
I was in a similar position with a house where the sellers backed out, having pressured us to sign our part of the contracts. Turned out a domestic dispute between partners, she refused to move out of the house so the sale had to be called off.
Twice I have had the original estate agent and another estate agent coming back to us asking us 'if you could get that house for X amount would you be interested, he's thinking of selling it again'.
If you made an offer, you could always see if you could get the sellers to sign something to say they will cover your legal costs if they pull out of the sale if contracts have already been issued.