[dmsinnott]

Screw was on (very) tight, looks like the barrel connector from the handle that goes to the the raise/lower spindle in the assembly itself is either not fully engaging or is broken. When it failed, it failed quickly - the vent lid closed rapidly while I was holding the handle trying to open it. 

Just another project to add to the list. Good thing we as a group like to tinker. 

Thanks again for the information!