Problems with leakage in SEIS seismometer which is one of crucial onboard instruments on InSight Mars lander could threat all program.
Problems started on November 2015 when first leakage was spotted, but CNES specialists managed to repair it and keep the schedule. Unfortunately on 21 December 2015, when during test of SEIS performed by French scientist from CNES another minor leakage was found. Scheduled date for launching Insight on atop Atlas V was March 2016, but due the leakage, mission was postponed to next launch window on May 2018 (You can read more here). SEIS was CNES contribution to InSight program which was mainly developed thanks to NASA funds; according to CNES President Jean-Yves Le Gall group of independent experts is necessary to explain reason of leakage which caused 26 months of delay. But it is not the end of bad news: if Atlas V rocket booked for InSight can be utilized by another customer, storing whole InSight lander by NASA is not so easy. Lander needs ongoing maintenance which is expensive. NASA spent for program as main founder $525 million of the $675 million mission budget and it is possible, that for storing lander for over two years there will be sufficient funds. Now NASA could be forced to increase budget due the problems caused by its partner, CNES. Due the fact that cooperation is not based on common budget, all expenses related with storing InSight lander will be covered by NASA. Of course for CNES delay is also generating expenses - they were described by Jean-Yves Le Gall as 10% to 20% of CNES budget for InSight which consisted $54 million. It seems that InSight will be launched on scheduled May 2018 unless NASA will decide to launch Lander without SEIS (it would be rather nonsense) or decide to resign from InSight after spending $525 million (it is not sure which option is less common sense, but if additional funds are concerned nothing is beyond dispute). CNES stand in case of future of the InSight was officially announced on press conference on 4 January 2016, by Jean-Yves Le Gall, that Mars is still in focal point of CNES plans basing both on cooperation with NASA and ESA. It gives hope for a happy finale of the entire program.