Oof, quite a few!
One landlord didn't tell us that the oven had a hole in the bottom where it was rusted through and it was covered with foil when we moved in so we didn't see it. We realised when it caught fire. Took him 6 months to replace it.
Same landlord gave us 2 month's notice to leave because he lost the property in his divorce settlement. When the boiler died 3 weeks later he told us he wasn't spending any more money on the place because it was his ex wife's problem now and made us sign a document detailing all the things his ex wife had claimed he was doing weren't true (refusing access to the property, etc etc) 😳 Also the boiler died in November so we had no heating or hot water in the winter with 2 kids under 2.
A different landlord didn't do any sort of inspection or inventory upon moving in but then when we left charged us for things that were already there (eg, repainting for a whole room with a small scratch on one wall, professional cleaning, new carpets etc) all for oddly specific amounts that miraculously totally the whole exact deposit on the house. Funnily enough refused to provide receipts to prove these amounts had been paid and to who. I actually went back to the property afterwards (it was empty) and none of said 'repairs' had been done at all. He also changed the locks without telling us 2 days after we left and then charged us for a piece of furniture that was still in the property to be removed (we'd told him we were coming back to get it).
I refused to release the deposit from the company that held it until we could come to an agreement and was told to wait until further notice. 6 months later I was fed up waiting and it turned out my LL had put in a solo claim, saying that we had disappeared and he couldn't contact us. He was supposed to notify us of his intention to do this to give us a chance to respond. He did. He sent the letter notifying us to HIS house - our old house, ie, the one we had just moved out of!! He had our actual new address but purposely sent the letter to the old house knowing we would never receive it and he would receive 100% of the money. I was furious but was heavily pregnant and depressed and had no idea how to fight him so I just had to leave it.
Oh, he also tried to claim hundreds of pounds in rent from the council AFTER we moved out because it took him a few weeks to find a new tenant and as we were on HB at the time he decided it was our/the council's responsibility to make up the shortfall. The council laughed at him, told him it doesn't work like that and told him to jog on 😂