Insignia disaster

[matejxyz321]

I have Opel Insignia, 2.0, diesel engine (manual six-speed gearbox). At times, when driving in free-run, the motor cuts out completely. As a result the steering wheel becomes heavy; hence, if a driver is not alert, he/she can by no means handle it. After a moment (when the break is pressed down) the brakes also stop working. It does not happen often (once a year) yet it proves extremely dangerous. Just as an example, while driving at 90 miles/h in a dangerous situation at the highway. I pressed the clutch and put into gear. While in another situation I stopped the car and started the engine successfully with a key.
The Opel (original service) checked the problem yet could not find any problem. Also the car's computer failed to record any fault. I’ve received information (off the record) that regeneration problems might occur during DPF.
I contacted the Opel service (and they contacted the manufacturer) many times without any success…An accident should happen first probably …

Does anybody have any similar experience or idea how to solve the problem?