When to bail on this chain?

[endofthelinemaybe]

Offer accepted on our dream house in October, offer received from first time buyers for our house, our vendors said they would go into rental. Several months later they have decided rental unfeasible and so looking for house to buy. They've been looking for months, have offered on a couple, one fell down at survey, but very little communication recently. I think they are very specific, and possibly also finding the downsize from a big family house to a smaller but still quite expensive bungalow a bit tricky.
For us it's this house or we won't move at all and will extend.
We've sunk solicitor costs already, which is frustrating but tough luck for us.
When do we give up and pull out, or do we sit patient until our buyer pulls out.
It's so disappointing

Give them an ultimatum and stick to it? They’ll know it’s a Seller’s market so they can just re-sell. I think Buyers are having to wait around, the market remains strong.

Have you applied for a mortgage yet? If so, that's a good deadline to give. If not, rates have gone up so much since October 😬 I wouldn't be waiting around much longer

It's only this house for us, or we won't move.
They will easily sell again so an ultimatum won't really do anything-either they can find something or they can't.
Mortgage wise we have renewed our offer and it's a bit more expensive but still manageable and we have another few months before it expires again.
I just can't figure out if they are massive time wasters. They sound so genuine to talk to, but this is the second time their sale has fallen through, although last time they were waiting on someone further up the chain to find for months so they should know how we feel.
Saying they would go into rented and then not was a dick move, just don't say it. Funnily enough a Mumsnetter warned me that this is common and not to get my hopes set on it.
I think I can either wait on, for a sliver of a chance or bail. Either way I'm financially out of pocket. But emotionally feel like I'm not living in my house properly, not wanting to do anything to it incase we go, it's really annoying.

I feel for you.

We are in your buyers’ position. Again. It’s been two years now since we sold and moved into rented, and it appears that we are the one of very few to actually do what we said.

we even had one set of vendors’ vendors pull out on day of exchange. The vendors’ vendors had said they were looking to rent in a new area. The vendors had said they would move into a rented to keep the sale. Neither happened! We even offered our vendors some extra money to do it.

Currently in another chain of 3 (or is it 2 - not sure if it’s number or properties or people?) and expecting the same from the vendors’ vendors who said they are looking but will move into rented for the sale. Hah.

I just can't figure out if they are massive time wasters

We're downsizers and we’ve been looking for two years next month; I don’t know where you are OP but in our region there is no availability. Bungalows are very rare. It’s not being a dick, there just ain’t anything suitable to buy. And the rental market isn’t any better, there’s just no stock.

Your vendors may also be very wary of doing what we’ve done; sell, move into rented and then when they can find anything to buy, watch the market appreciate away from them another 15-20%. We’re able to take the hit financially, but if we needed that money to fund retirement then we would have been royally stuffed.

Our local market has gone quiet again so it’ll be September before it picks up again, and then it drops off about November till next spring. So you could have a very long wait.

It sucks OP. I think if I were you I might be tempted to stay and extend.

Mystery solved. Vendors have pulled out. What's really got to me is that If she hadn't bullshitted us about going into rented at the beginning none of us would have instructed our solicitors until the chain was complete. Instead ste let us get months down the process then said ste was going to start looking. We are all thousands out of pocket. Selfish, selfish woman.