Parents have seen their children's names mysteriously drop off the disability scheme's MyPlace web portal and lost records of previous claims as the Coalition government says the system's key problems have been fixed, two months after the debacle began.

Some participants in the billion-dollar scheme have even been left out of pocket since the troubled national re-launch on July 1, with the hamstrung National Disability Insurance Agency indicating some refunds could not be given for months due to a new inflexibility of amending individuals' plans.

The ACT Disability, Aged and Carer Advocacy Service chief executive Fiona May said a particular concern was the "enormous stress" participants were under, claiming the insurance agency had under-acknowledged the human impacts of the failures.

"I have had conversations with people who have shared that they have lost sleep, been unable to undertake other activities, withdrawn from friends and family and had poor mental health as a result of the portal failure and its impact on them," she said.

"There is no doubt that the NDIA failed spectacularly in communicating the system failure, and their progress in correcting it, to people who have been affected."

Ms May said the more than 500 Canberra participants who self-managed their NDIS plans had all been affected, and it was likely most of the additional 1000 who self-managed parts of their packages had been hit also.

Karen Hedley from Gungahlin has two children with autism on the NDIS and is a participant herself due to her chronic physical and psychological health conditions. She said she had not been able to lodge any claims since July 1 and as a result spent $1500 of her own money to continue support from a physio and exercise physiologist. The NDIA also owed about $2000 direct to a service provider for support workers for her and her children, she said.

"As a single mum working in the community sector I don't have much money. It's incredibly stressful."

Melinda McFadden and her two boys have each been using the NDIS since October and together have first-year plans worth more than $160,000. But for the last three weeks one of her sons has dropped off the system without explanation and inconsistencies in account balances have made it extremely difficult to work out how much is available to spend. Many dozens of hours have been spent lodging manual forms and seeking advice from the insurance agency, and she intends to stop self-managing the NDIS plans as a result.

Social Services Minister Christian Porter, who ordered an independent review of the launch problems by PwC in early August, said interim information showed two issues from July. The first was a technical systems issue which saw multiple claims for payment from bulk service providers fail if information for one single claim was incorrectly logged, and the second was inadequate information being provided to users of the portal, leading to input errors.

"In the first several weeks of operation [in July] the successful claims averaged 70 per cent. This situation has significantly improved and the rate of success for all claims in the past four days is now over 96 per cent," he said. There had been more than 83,000 successful individual claims in the four days. The review was due to be finished by the end of August.