Sold Our Camper And Now Getting Sued Will It Fall Through?

Location: IL
So my fiancé and I sold our camper yesterday. When we lived in it we had hauled it, stayed at campgrounds with it, plugged it in, and there was never electrical or wiring issues. When we decided to move out we listed our camper on Facebook Marketplace. My fiancé listed what was wrong with it two broken or cracked windows, a tire that doesn’t hold air too well, and the ceiling in the master bedroom was off due to leaks from the past. That were the only issues we KNEW about. A guy messaged my fiancé and they both settled on $1,200. The guy came yesterday and was looking at it on the inside and outside for about an hour with my fiancé everything seemed to be fine he gave the money, my fiancé helped him hook it up to his truck, they were having a bunch of conversations about random shit. But at 1:14 AM my fiancé gets a text (we didn’t see it til this morning) this guy was hauling the camper back home and it caught on fire, 10 miles away from the original place the camper was at? Which already kinda seems like a lie because we got done with the sale at 7, you’re telling me it took you 6 hours to get 10 miles? But anyways he said the fire department said it was caused by faulty wiring in the back bedroom. But then he also said the fire department said he thinks there was a rats nest in the electrical box. We’ve never messed with the wiring, when we plugged it in at the campgrounds and when hauling it everything was always smooth sailing. He’s saying he wants his money back which I understand but the sale was final. He signed the title and paid my fiancé for it already. There were no issues with it that we were aware of so we are not liable for what happened. The guy was at the camper looking at it for a good minute he should’ve checked the electrical box, wiring, anything like that and I guess he didn’t. Or when he did there was nothing and now he’s just trying to get money out of it. He was bragging that he’s won 6 lawsuits already which is why I’m assuming he caused the fire to get money from us. I’m just so confused tho because there’s never been issues, we didn’t have any wires sticking out in the back room, when we lived there our cats would fuck up some rodents so idk but he’s trying to make us pay over 5k for everything! I don’t think we are liable for what happened. I’ll post the messages in the comments if it’ll let me. But legal advice please!!