If you continue to carry on using the lock there is a very good chance the lock will fail and the worse case scenario, it can fail in the locked position when you’re outside. This will mean getting a locksmith to not only get you in but also most likely change the whole locking mechanism, which will be inevitable an expensive affair.
You can adjust the PVC, PVCu, uPVC door by first opening the door and try to lock the door in the open position, if it works fine then the problem is with the keeps or door adjustment, the lock is fine.
While making this uPVC door adjustment, if a handle does not move take a look at the face of the lock near to the latch and see if there is a small plunger sticking out. This would normally be depressed when the door is closed so to check the lock push this in with your finger and then try lifting the handle, if its easy to use then your locks fine.
If your lock is stiff in the open position the lock has the fault, it may only need lubricating so pour a few drops of 3in 1 oil along the strip and adjust the uPVC door.
UPVC doors can be adjusted by a technique called "toe and heeling" as well.
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