If key turns full 90 degrees from vertical to horizontal try pushing in really hard on lock housing while pulling out on the paddle. Had similar problem and that is what worked for me. Once opened disassemble lock and check latch bar to see if bent. It will take some bending before metal fails. lube moving parts. If latch bar still sticking try adjusting the four inside screws - one corner screw a bit loose can make a big improvement in how freely latch slides. I have developed habit of pushing in on housing every time I open a basement door. I have been lucky and not had to drill one. The biggest problem is service techs plugging coach into power with cord thru door and the closing door on the power cord. That bends latch bar.
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