Just to share some experience.....
This senario is very common.. Although the COC says that we can forfeit the PBond (which is also 5% of the Contract Sum)..but then Pbond is actually to tackle defects work.....what if there are lots of defects and at the same time a design failure?
D n B in most cases are big projects,......DBond is required to be submitted upon issuance of CPC. At this point of time..if the contractor failed to submit the DBond......try to withhold any other subsequent paymenst.!!!!!! It may helps.
Well...it works in my project anymay.....give a try.