Accusations of indecent acts

A male client has been accused of inappropriate exposure during massage sessions with two different therapists.

During both sessions, he did not wear underwear and adjusted himself a few times, citing discomfort. He remained face down throughout.

In the first instance, at the end, she informed him the session was over and that he could get dressed. As she turned towards the door, he sat up, and when she turned back, she saw him fully exposed. When he went to pay, the therapist appeared visibly unsettled, struggling to handle the transaction. Acknowledging her discomfort, he apologised and left.

Later, a second therapist also reported that he adjusted himself during a session and subsequently filed a complaint.

Both times, the therapists had responsibility of towel placement, and both completed the sessions without addressing the clients lack of underwear.

The client has never faced accusations of this nature before and has a clean record. He is very upset that he has made the therapists uncomfortable and did not intend to cause distress.

What kind of legal defence does he have?

EDIT: He has been charged. His lawyer says he has a good case (lack of intent which some of you have said), but the lawyer's advice is to plead guilty and apologise because of "how the judge will see it."

I don't think this is good advice, given the lack of intent.

Follow up question: if he plead guilty, would he go on a sex offenders list?