Please tell me, could ocd cause difficulty understanding what people are saying?

Possibly: If the ocd messages that are directing the individual on a fairly constant basis, it's like trying to have two conversations at once. The interference would make it hard to understand people. Especially complex interactions would be quite difficult. You are wise to recognize this and i hope you can find a good therapist to help get the ocd under control. It's not easy, but it is possible. Best!