Z6600 Needed a belt and I made it worse

[bottleworks]

Hello! My HP Z6600 was working, but had a fraying belt. I replaced the belt and now it appears to jam once it starts moving the carriage fast. I suspected that I must have somehow damaged the encoder strip, so I replaced that. It made no change. It moves the carriage normally from right to left and back right again (slowly) completely normally. Once it starts moving faster, it jams. It doesn't jam at the same place. It's typically in the right 1/4 of the total travel. With the machine off, I can slide the carriage without any snags, or anything unexpected.

A quick video clip of the printer:

I then stumbled upon: https://h30434.www3.hp.com/t5/Desig...iage-Belt-Replacement-Issue-with/td-p/7024429
They had the exact same issue as I'm having.
As an experiment, I tried flipping the inner bracket (which holds the idler) upside but keeping the outer U bracket in the same position. (You can't install the U bracket wrong because it hits the encoder strip). When tightening the screw it binds on the inner bracket and kicks the tensioner like shown in the link above.
Now the machine works. BUT! Clearly this isn't correct. It works, but it's still broken and wrong. I know I had the tensioner correctly configured (per the service manual images) prior to this test.
So, I don't like to halfa$$ things and would like to get to the root cause. Maybe the belt is slightly too short? Ideas? Thanks!

 

[maximumapogee]

Belt looks too loose or too stretchy. Is it a genuine HP belt? Bought a Boracell belt off amazon once, and had the same problem. Make sure the pully bracket on the right is all the way up against the end piece.

 

[ToTo]

Have you re-mounted the black plastic stopper on right hand? The original belt comes preassembled correctly. On the u-bracket you have to holes. The round shaped should be on the bottom pin.
If the encoder is correctly mounted there should be a gap of about one millimeter to the bracket corner.

 

[ToTo]

But the fact that you reassembled it means you bought just a naked chinese belt. And yes the tension is poor.

 

[bottleworks]

Hello.
Yes it is an eBay belt, but I believe a key thing is missed. With the tensioner assembled backwards, it reduces tension on the belt. With that lower tension, the machine operates correctly.
Yes, the carriage stop is installed.

 

[MonsterBabyBLN]

make sure you have the carriage on the exact same position on the belt as before!.. you can count the notches.. I think this is important, too!