Help! This house is a millstone round my neck.

I may not get any sympathy here because the house in question is a holiday home. In my defence I used an inheritance from my DF to buy a cottage in North Yorkshire with DH about 20 years ago. At that time DH had his own business and couldn’t take much holiday so it was a way for us to have short breaks only an hour from home.
I loved it and considered moving there for retirement, but after DH sold his business shortly before lockdown he seemed to have a personality change. He said he felt he didn’t fit in there and started obsessing about buying a property on the lake back in Northern Ireland where he comes from, and where he could sail.
At the time things were bad and I thought we might break up and even if not I welcomed the idea of him being away from the family home if he was in Ireland sailing.
We sold the cottage in Yorkshire and as prices are a lot lower in Northern Ireland we used the money to buy a large house overlooking a lake on a holiday complex in Fermanagh. I also had enough money to put in a new kitchen and renovate the family home. The house in Northern Ireland was put in to DH’s name for tax purposes as we thought we might rent it out.
Things haven’t worked out though. DH has been diagnosed with mild cognitive impairment which might explain his personality change. It may or may not develop into dementia but at present he is functional but has not wanted to come to Northern Ireland without me, and the boat he bought remains unused. Our children don’t want to holiday there unless I pay for their travel because it is a long, expensive journey and the weather is often poor.
It costs us several thousand pounds in bills and site maintenance every year. Every time we come there is an issue - last year there was a leak, this time the boiler broke down. I have now got him to agree to sell it, but everything moves at a snail’s pace here and it’s all down to me to sort out.
We thought we had a perfect solution in that the daughter of one of the people who runs the management company wanted to buy it but it turned out after stringing us on for a month she couldn’t raise the money. Someone else may be interested but this morning the mother of the girl who wanted to buy it came round. She is also a director of the management company. She raised an issue about boundary lines and whether our shed was on next door’s land. I am enraged - now we know there may be an issue it could jeopardise any possible sale and I can’t understand her motive- is she trying to delay everything until her daughter can raise the money? I said that as far as I was concerned the shed was on our land. She said she would get a surveyor to look into it. WHY?- what business is it of hers, the house next door was sold last year and presumably if it was a problem it would have come up then.
The worse thing is that DH doesn’t understand the issue, he keeps repeating that she gave him permission to put up the shed. It will be down to me to sort out, I’m fed up, I didn’t want this house and it was bought with my money from my inheritance.
I think I just have to suck it up - has anyone got any advice?
Good just to vent though.