Yep, this happens several times a day at my house.
I used to repeat my question 3 or 4 times until he managed to answer it. Sometimes I’d add a passive-aggressive ‘Or’ at the start eg:
Me: do you know where the secateurs are?
DH: yes, you’re right, the roses really could use a prune.
Me: Or, do you know where the secateurs are???
Now I just stand there, staring at him, until the awkward silence prompts him to reconsider what I actually asked.
Our 7yo gently pushes him into a chair, puts her hands on his shoulders and stares deep into his eyes, if she needs an answer to a question. She speaks slowly and enunciates dramatically, as one might do to a person with significant brain damage.
Lord knows how he manages to run his business.
The only insight I have, is that he runs more on feelings than logic. He confronts conversations as if they are a piece of music, rather than an attempt to elicit actual concrete information. He reacts to the speaker, not the words. He utters whatever his feelings have evoked in himself, and having heard himself speak, decides that the conversational form has been achieved and can now end. That is, I said something, he said something, job done.
My mum is similarly frustrating to speak to, but I think something different is happening. With her it feels like her brain is full of trains of thought (I picture these as actual trains) rushing about in a random chaos (fuelled by generalised anxiety, I fear). If you ask her a question, a bell rings in her head. A random train will pull into a random station, and unload its cargo. The answer you get will be nothing like on topic. The Surrealists would have loved her!
I used to think I was going mad, talking to these two. Now my DD and I take solace in each other’s logical minds!