The trains were delivered late, and were put into service after the Norwegian Railway Inspectorate had given dispensation from parts of the safety regulation.

The class was grounded for a month, and the investigation showed both design errors, and lack of proper inspection and testing.

The reports concluded that there would have to be invested 56 billion Norwegian krone (NOK) in new infrastructure if the main corridors were to be built as high-speed railways.

When issuing invitations to tenders, NSB specified this time limit as a criterion, which was also the reason the line was dimensioned for 210 km/h (130 mph).

[5] Proposals had been made for NSB to purchase the same units as the Swedish State Railways (SJ), the X2, in a Nordic cooperation to use the same trains in Norway, Sweden and Denmark, but the idea was abandoned.

In May 1995, Osmund Ueland was hired as director-general of NSB, and he scrapped all plans to build new railways, and instead decided to focus on tilting technology.

[6] Compared to X2, Class 73 has an upgraded bogie construction and motors in multiple cars instead of having a locomotive unit.

The latter forces a four-car configuration, but allows for better traction and better use of space and weight by placing the technical equipment throughout all four cars.

To take advantage of the faster speeds, the Norwegian National Rail Administration needed to do upgrades to the track, overhead wires and signaling for NOK 1.2 billion.

[10] The inspectorate had a series of safety concerns, including follow-up on the safety terms for the wheels and axles; lack of documentation of the crew's training; denying NSB's request to have fewer inspections and less maintenance on the trains; lack of consideration of critical events deemed to have a high probability to occur but have a low consequence; lack of a safety inspector for operations and maintenance; and that the trains were so heavy that they would exceed the permitted axle load of the lines.

[12] On 28 October 1999, Minister of Transport Dag Jostein Fjærvoll asked the directors of the three involved parties, Osmund Ueland of NSB, Sverre Quale of the inspectorate and Steinar Killi of the National Rail Administration, to meet at his office the following day if the issue was not resolved.

NSB stated that a contributing cause was the previous year's mild winter, which made it impossible to test the trains in extreme weather.

[15] On 16 December 1999, NSB confirmed the option for another six Class 73 trains, costing NOK 680 million, for use on the Østfold Line.

He stated that the Sørland Line was extreme in Europe in the number of curves, and that this gave increased stress on the axles.

He further stated that NSB had controlled only part of the axle and that if proper tests had been made, the fatigue would have been discovered.

[29] On 26 June, NSB stated that in April they had discovered that not checking the whole axle was a weakness in the maintenance procedures, but that despite this, no new examinations had been done.

[37] In mid-August, the tilting mechanism was disabled on all the trains because of a fault in a bearing in the connection between the bogie and the body which allowed for a movement of several millimetres (at least 0.1 in).

[39] The cause of the cracks was a rubber washer which had been installed on the first eight trains—rather than the conventional plastic cover—which was intended to protect the axles from ice and stones.

On 30 August, NSB gave Adtranz two weeks to solve the axle issues unless the contract was to be revoked.

[42] In mid-September, the press announced that on 8 May 1996 NSB had agreed that Class 71's axles could receive a steel quality substandard to European standard and recommendation from the International Union of Railways.

The reason was that the class would have a much higher weight than planned, and that this would cause the trains to operate more slowly and thus not be able to reach the airport in the desired 19 minutes.

[45] The parties continued to disagree on the size of compensation Adtranz should give NSB, with NOK 100 million separating the two.

[53] The B-series was originally put into service on the Sørland Line between Kristiansand and Stavanger, as part of the brand Agenda.

[54] The B-series had been planned for use on the Østfold Line, but because the latter is largely a commuter service with many standing passengers, the company was not comfortable using the trains there until the issues regarding the axles and wheels had been resolved.

NSB stated that the new class would offer better comfort and reduce the railway's problems from delays caused by icing.

In particular, a DNV report from 1999 had shown that the train could act as a sled, lose contact with the tracks and slide on top of the snow.

However, the carriages were at the time being used on regional rush-hour trains around Oslo, were in need of renovation and did not offer the facilities required by intercity travelers.

[62] In October, NSB stated that they planned to withdraw Class 73 from service on the Bergen Line, because the use of multiple units was not flexible enough.

The driver immediately applied the emergency brake, which caused the train to stop 5 to 10 meters (16 to 33 ft) from the fire.

[68] The first set was to arrive in May 2014 for inspection, scheduling of the works involved and evaluation of the process while the remainder of the fleet would come in from spring 2015.