Background:
I have a friend named "Joe". When talking to him through messages it feels like he drops off mid conversation. On several occasions I asked him a direct question like "when are you back from vacation" he doesn't reply at all. He replies to the next question. Other people notice he does this as well. Another example was he told me he liked his new home and how it's a lot different than his old one. I asked different in what way and he never replied.
What I tried:
when I was with him I told him I find it rude when someone does not answer a direct question. He agreed. I mentioned I feel like he sometimes doesn't reply to my question. He said "when did this happen?". The only example I could think of in the moment he had a valid explanation for so it wasn't really constructive.
Considered:
It was him that got this friends group into using a specific messaging app he likes. It supports read receipts but he has his turned off. I'm wondering if all this is some sort glitch and he isn't getting some messages. I've waited days and got no answer.
What I am looking for:
Without making him feel defensive how can I find out why he doesn't respond? If it's a technical problem maybe it can be easily fixed. If he prefers phone calls, that is fine. If he doesn't like talking about certain subjects, I would like to know the subjects so I can avoid them.
I am looking for answers with actionable advice. Please don't reply with "this isn't possible" or "you can't do this". Thanks.