Reply by DannyB

The belt slap is “normal” on this machine¹, but it can be fixed. At least in my case, i replaced it with a properly tensioned link belt and get no slap anymore. I’ve seen a number of solutions.

Someone on another forum also claimed griz tech support told them the shudder-on-stop was a harmless motor issue².
Mine doesn’t do it, so i can’t help you there.

[1] If you google search, you can see the belt slap on this machine has been complained about since late 2007.
[2] http://www.woodworkingtalk.com/f12/new-jointer-vibration-g-0490-griz-14493/, search on the page for “returning to zero”