score:4
This is covered on the CFR Calatori website, under "Sleeping and berth car":
» Not presenting at the car when leaving the boarding station
When the passenger is not present at the sleeping or berth car, to occupy the seat within 1 (one) hour from the departure of the train at the boarding station (indicated on the bed / berth supplement), the seat is considered to be free (art. 49.4 Uniform Norms for Romanian Railways, approved by OMT no. 655/2007, as subsequently amended and supplemented).
That means that for the Dacia Express, which has a departure from Bucureşti Nord at 14:50, if you do not reach your berth by 15:50 by the latest, the reservation may be considered lost and may be sold again. It is therefore NOT safe to board at Sinaia (16:14) or Azuga (16:29), but you should in theory be able to board at Ploieşti (15:27) or even Campina (15:49), provided you reach your berth immediately. The safest, however, is to board at Bucureşti Nord as indicated on your ticket.