Industry sources have said the 147,000-cbm Dapeng Sun (built 2008) will remain at Sembawang Shipyard in Singapore for repairs until the end of July.
The yard has been trying to resolve microbiological contamination of the ship's stern bearing oil, which has resulted in the need for frequent filter changes.
But those nofollowing the repairs say other problems such as vibration issues are lengthening the repair job.
The Dapeng Sun arrived at the yard in mid-June. Work on the vessel, which is employed shipping cargoes from Australia's North West Shelf project into China's Guangdong LNG terminal, was due to take between 10 and 12 days with the ship set to return to service early this month.
Chinese players are blaming the delay on manager BP-led China LNG Shipping (International) Co (CLSICO). They argue that complications have arisen because Sembawang is not "familiar" with the ship and say the work could have been done quicker in Shanghai.
They say Hudong-Zhonghua Shipbuilding, which built the Dapeng Sun, offered to undertake the repairs. However, CLSICO is understood to have been adamant the ship would not return there.
CLSICO, which is managing all five Chinese newbuildings - two of which are set for delivery this year - has already said that issues seen in the vessels' operation can be traced back to poor housekeeping during their construction.
Hudong-Zhonghua is also expected to receive an order for a sixth vessel shortly to be jointly owned by China LNG Shipping (Holdings) and Malaysia's MISC.