Folios: tell me why please

Good evening peeps,
I am just restarting on the lengthy process of buying another property in Ireland. The last one fell through when I discovered so many irregularities that I'd be here all day explaining, but suffice to say that I was forced to return to the UK licking my wounds and very much poorer.
This time I am determined to do this properly and make sure no one pulls the wool over my eyes which results in yet more money being wasted as I simply can't afford it.
The property I am interested in is being sold privately and the current owners are very keen to return to the UK. They don't need the funds to buy their house back here, but are determined to get what they paid for their cottage a year ago.
The property has a few acres attached to it, and this is the biggest reason for my choice of property. It is also absolutely vital to my financial wellbeing that the acres belong to the property. However, the land registry is stating that only half the land belongs to the cottage, and the other half is not theirs. I have spoken to them about this and they have stated that the other half, which oddly enough is the half nearest the cottage, was purchased at a later date (not by them) which is why it's a separate folio. I'm not convinced as surely if the land was owned by the cottage, then it would all appear as such on the land registry maps. Instead it is coming up "unknown".
Has anyone come across this? My gut is saying that they are not to be trusted and I should walk away now before I incur more expense.