Happs Ultimate sticking?

[StormGiant]

I'm modding a Happs Ultimate 8-way stick with an old Microsoft flight stick handle.  Took apart the Ultimate to get the joystick handle to fit into the handle grip of the old flight stick.  Now the joystick is working poorly.  The Z-stop on the joystick is getting stuck in the bracket hole.

My other joysticks are Supers and the Reunion.  On this Ultimate, unless I'm missing a mystery part or putting it together incorrectly, it seems poorly engineered, as if either the Z-stop diameter isn't large enough, or the hole in the bracket is too large, allowing the sides of the Z-stop to fall through and get stuck.

Anyone else have this problem?  As a solution, I was thinking of putting a 1/2" nylon washer in there, but haven't tried it yet.  Reference is this http://www.happcontrols.com/joysticks/507608xxx.htm page.