It is most likely your xc time faults.
There will have been either a time allowed or an optimum time.
If there was a time allowed, you will have gathered time penalties for every second over you were (BE rules are 0.4 penalties per second but 1.7 doesn't quite fit for this, would be either 1.6 or 2?)
If it was an optimum time, you would have gathered penalties for every second under or over the optimum time.
