One thing always gets me with a lot of American machines.
The screw down lid for the waste chamber, I've always favored the dome which sits tight with the vacuum pulling it down, simple to release and open without getting screwed, simple to replace, a rubber seal retains the vacuum.
Sometimes grit gets under the gasket creating an air leak, also the screw can become bloody tight when trying to open it with sweaty hands.
My biggest bug though is the habit of locating the switches at the rear of the machine when all the plumbing is at the front.
Many people leave their porty in the van with the plumbing facing out, this makes turning these switches on/off bloody difficult.
Waterproof rocker switches are available for this role.
Just a little bit of constructive criticism from down under.
Shorty