First thing I would do is remove the bevel gear on the crank wheel side and turn the jack screw side by hand, testing to make sure the saw assembly runs up and down smoothly.
Mostly though I suspect the bevel gears. What I’m seeing looks like they’re meshed incorrectly/too tightly. Try any adjustment to move them relative to each other, ie back them away from each other slightly. I can’t tell if the shaft bosses have any adjustment or ability to loosen them; if they do I would loosen them slightly, turn the handle to see if the gears find somewhere they like, and then tighten it back down. Looks like it’s a simple cast assembly though.