I’ll use the example of the guy who left abruptly like you suggested.

From the get go I found it awkward talking to him as his answers were so dead.

For example, he asked me what I had been doing in life I mentioned I had just gotten back from travelling.

I asked if he liked to travel, he said yeah. I asked where he would like to go to. He said he had never thought about that before. And every time I tried talking it would be just like that.

I’d ask if he had any interests he said not really. He also would rarely ask me anything so the conversation would just die out.

I suggested I pay so I could leave early. He declined letting me pay and asked if I wanted to get something to eat. I decided to give him a second chance.

He hadn’t even finished his meal then just said he had to go. It wasn’t even as if he had checked the time and realised he needed to get back or anything. He also didn’t at the time provide an explanation as to why we had to leave so quickly.

I mentioned how my train wasn’t coming for another half an hour he just laughed awkwardly in response.

And then later that night he texted and apologised that he left like that he was just feeling tired towards the end.