Screw them all the way out, take a wire brush, clean the threads on the bolts and the holes with solvent, replace any that are stripped, grease them thoroughly and then they will go down and not stick.
Haven't had a problem since I made this part of my opening routine. A tub of general-purpose or white lithium grease works great.
I had some stuck and stripped ones before I learned to do this, and I used PB Blaster and clamping on vice grips and banging them around with a hammer to get them out. You could also try applying some heat with a blowtorch.
Hope this helps.