Hill master patio door handle and lock

Thanks for posting. It sounds like the mortise lock in the door may be damaged, so it is not staying in the locked position. To test this, remove the handle set from the door and try manually 'throwing' the lock with a slotted screwdriver. If it doesn't budge, then you know the lock is indeed broken and the culprit. If it works fine, then the issue might be that the lock and keeper are not aligning correctly. Either way, we will need photos of the mortise lock and your handle set to confirm the parts you are working with. We'll do our best to find potential replacements from there. 

The mortise lock is our 82-226. Check the handle set and thumb lever just to make sure it isn't damaged. If not, and if the mortise lock does not budge manually, then replacing the lock should do the trick. Let us know if you have further questions.