Use a phillips screwdriver to screw in the loose screws or tighten a loose plate.
Thumb press door handle sticking.
Turn the knob to open the door and release the knob slowly.
You should first test the door latch to ensure the latch is sticking inside the door and not due to a misaligned strike plate.
If the door knob lock button is still stuck try turning the handle while experimenting with the ways you are pressing the button.
This is for when the door lock button is stuck in as this is often the most common type of door button sticking.
This is because the issue is not with the door and not even with the control the knob has over the stuck latch.
The thumb latch feature on older handleset mortise locks were never terribly efficient it was usuallthe second thing to fail after the inner knob would come loose due to inadequate set screw issues.
Open the door and look for obstructions in the door lock plate like loose screws.
Repair info for baldwin images style handleset issues why kwikset handlesets stop working right as well.
Jiggle the handle more vigorously fast though not with too much force if you are not getting results.