I have been extremely lucky that in 20 years and 4 property moves, I have never had the chain collapse near exchange.
However I have been tearing my hair out in the week leading up to exchange. Every time.
First time I bought, the vendor had said they were moving into rented. Then changed their minds without telling anyone and put an offer on a property the week before exchange. It held everything up.
When we finally completed, a week later, we could not get them out of the house, it was 9pm before they left.
We sold that house and bought a brand new property. The people who purchased it were relocating to our area and the day before exchange decided they wanted a full survey dine on our house. Holes drilled in our walls etc, for no reason at all. If we had waited for this, we would have missed the deadline on the new property. I lost my rag and told my solicitor that they could tell our sellers that they either exchanged the next day, or we would pull out. We were going to lose our new build if they didn't exchange. Thankfully, the sellers went ahead with exchange. Turned out they were time wasting as they didn't want to move for another month.
Third was a shit solicitor that nearly broke me.
This year me and exdh sold the marital home. It took 20 weeks to exchange. I was effectively homeless and sleeping on a friends couch with 2 kids. On the day of exchange I was told I would be kept updated. I called at 3pm as I hadn't heard from anyone. My solicitor told me she had held up exchange as she wanted me to confirm, in writing that I was aware of how much money I was getting. Except she never bothered to tell me that. I wrote the emajl while she was on the phone and told her to get on with it. Another shit solicitor and I ended up getting all my fees back as this wasn't the only time she forgot to do something.
The house I am in now, had someone further up the chain that was dicking about. Again I was still on my friends couch. The first exchange date, came and went. I told my solicitor to contact whoever was messing them about, and tell them if we didn't exchange on the next agreed date, that I was pulling out and going into rented accommodation. I couldn't continue living in the circumstances I was. Shockingly, they all got their fingers out and we exchanged.
Again, could not get the vendors out of the house. At 4.30pm, When I knocked on the door to ask how long they were going to be, the vendors mother got arsey and quite abusive. The vendors were nowhere to be seen. I was really overly nice as I didn't want to ruin moving day for anyone. She carried on being horrible, telling me to 'fuck off and come back when you are told you can'. I was so happy to was with me to witness her behaviour. In the end I told said 'that's fine and stood in the doorway and called my solicitor who just said 'that's fine I'll call their solcitor and tell them we will look at breech of contract and if she swears at you again, call the police.' Then told me to repeat back what she said. The woman's face dropped, the vendors turned up 10 minutes later apologising and they were gone within half an hour. Their solicitor had called them after to speaking to mine.
It's been a farce every time. Something has to be done. I nearly had a nervous breakdown buying this house. I don't think I could face moving again.