For me, it's just mild enough that I'm always expected to say the right thing, so people try to take me literally regardless of what I say. This wouldn't be so annoying if I hadn't a pet-peeve for accuracy of information.
Only sometimes. Half the time it's due to my dyslexia. The other half is too much on my mind and I mix words up with what I'm thinking and what I'm trying to say. It's not bad and it just randomly happens.