How to remove lower wash arm for Quiet Partner I?

[TheWilldog]

Hello, I'm trying to remove the lower wash arm to get to the filter at the bottom of the machine, but I can't seem to remove it.  I've spun the little plastic cap at in the middle of the arm around and around, but it doesn't seem to be getting looser or tighter, though it's really snug right now.  I have to use pliers to turn it.  What else do I need to do to get the cap off and the arm out?

Model DU1055XTSS2

[tgoods]

It's left hand threaded so turn it clockwise to loosen.

[TheWilldog]

No dice, the little threaded cap just spins without making getting any looser (or tighter).  I am holding the arm in place, so I don't know what else I can do.

[JWWebster]

Maybe this will give an idea:

Cool video wrong dishwasher dang it.

[AJ]

JW, after looking up his model number I believe this video is more like the dishwasher they have.