My Territory has gone into "limp mode"

We bought a RWD Territory diesel in 2012 to tow a caravan. On the first week of owning it, it went into "limp mode."

The dealer said it was due to the radio not being programmed properly. Since then we have done 49,000 km without trouble until recently.

Whilst travelling at 90 km/h on the freeway it again entered "limp mode." We turned off the freeway and restarted it and it returned to normal. We took it back to the dealer again who 'fixed' it. 

Later this year we drove to Queensland without issue, but on the way back it again entered limp mode on four separate occasions. The screen also displayed a DSC fault.

The dealer said that they could not find an issue and that the computer only stores faults for 12 hours.

They want me to drive it until it happens again and bring it in the same day. However this is a frightening and dangerous experience if it happens on the freeway or in heavy traffic. Can you advise if there is anything else I can do?