A Transavia France Boeing 737-800, registration F-GZHS performing flight TO-3174 from Paris Orly (France) to Valencia,SP (Spain), was climbing out of Paris when the crew stopped the climb at FL250 reporting some technical problem, the aircraft continued in the direction of Valencia while the crew were working the checklists. The crew subsequently advised of pressurization issues, maintained FL250 and returned to Paris Orly for a safe landing about 50 minutes after departure.
The rotation to/from Valencia was cancelled.
The occurrence aircraft is still on the ground at Orly Airport about 17 hours after landing back.