Daniel Joseph Dives pleaded guilty to two counts of failing to comply with his obligations under the register, which he was put on in mid-2017 after he was captured deliberately masturbating on a Wollongong train in front of a 16-year-old girl.

Court documents said Dives lived with an acquired brain injury after his involvement in a car crash in 2008 and suffered from memory loss and epilepsy, but had also abused illegal drugs in the past.

However, police said it wasn't an excuse for Dives' lack of reporting, especially as he'd been reminded by Community Corrections staff two days before he moved that he needed to contact police and update his address.

When police attended Dives' new address - only known to them because they had received an alert from Community Corrections - officers asked Dives why he hadn't told them about the move.

"I thought [the Community Corrections staffer] would have told you," he said.

"That's your job," officers told him, to which Dives replied "I have a brain injury."

In documents tendered in court on Tuesday, police said they also had no idea Dives had a new phone number, which he was required to report to them under the conditions of the register.

Dives' lawyer told the court he relied on his support worker to help him keep appointments and had only missed the window for reporting his change of address to police by two days.

Magistrate Darryl Pearce said the crime didn't warrant a jail sentence but convicted Dives and placed him on a 12-month community corrections order.