Faults forcing the near-closure of all the north's MOT centres came out of the blue, an official has said.
Cracks in vehicle lifts were first detected in November but the problem rapidly escalated this month.
Paul Duffy, chief executive of the Driver and Vehicle Agency (DVA), ordered the halting of most tests on Monday after failing to receive adequate assurances about repairs.
Julie Thompson from Stormont's Infrastructure Department said: "This has come out of the blue."
By earlier this month signs of cracking were detected in 48 of 55 lifts.
Taxis and four-year-old cars are being prioritised for roadworthiness tests following the partial shutdown at test centres.
Heavy goods vehicles and buses are continuing to be tested because they do not involve use of lifts.
Ms Thompson told Stormont's infrastructure committee: "Yesterday came as a big shock, the fact that the supplier said they did not have sufficient assurance over the repairs that were in place."
She said the parties involved need to learn lessons for the future to prevent the problem from recurring.
Sinn Féin committee member Raymond McCartney said: "If you bought a new car and there were 48 faults within a short period you would be back to the supplier saying this is not the car I bought and it is under warranty.
"Forty-eight lifts, all cracked - there is a design fault or something.
"People will ask questions as to why it was not picked up earlier."
Damage was detected on the scissor arms of the lifts, which were installed in 2011 or 2012, Ms Thompson said.
She added the department might have to buy new equipment.
"When you are in a position whereby this has never happened before, this is very fluid and very recent."
MoT exemption certificates lasting four months will be issued to those affected so motorists can continue to drive.
They cannot be created for four-year-old cars or taxis.
