Problem with UBA 10 JCM Billvall in my Bally Alpha V32

[Zingsi]

i have a Bally Alpha V32 Video Slot - inside a UBA 10 Billvall from JCM - when i start the slotmachine, the Billvall goes mad and tries to transport Bills on and on(without taking any)
i cleaned it, made a ram clear, without any change.... the Errors are: Stacker Jam, Billvall Jam .... but the box and the Billvall are empty and nothing is in it!

On the frontside there is a red LED which flashes every two seconds.....and doesnt stop!

Does anyone has an idea, what the problem could be?
Is the BillVall and the sensors perhaps BAD?

thx for helping

[Sunrise Side]

In the NLG File System there is a download for a UBA flip card with test and error codes.

[Stayouttadabunker]

There may be two clear plastic optical eyes on either side of the bill box.
What happens is the head shines infrared light down into one side of the bill box.
The emitted light goes around through a clear plastic molded channel inside the bill box and comes out the other side back up into the head into a receiver optic to verify that the bill box is in position....you need to get the dust off of the ends.
Also, if there's dust on a "stacker leg" inside the bill box, the infrared light doesn't get thu to the other side, and the head throws out all sorts of errors.

This "stacker leg" is a clear plastic post...looks like a triangular-looking stick in between both ends of the infrared optical channel plastics...you have to get the dust off of it.
Some guys actually throw the plastic bill boxes into a washing sink and spray hose the crap outta them...others put them in a dishwasher, while others know how to point the straw of a compressed air can onto the "prism leg" to get the dust off.
I use Q-tips with a long foreceps to reach down and rub the dust off of the prism leg.
Do not use any cleaner that contains alcohol....the alcohol actually degrades the plastic optics blurry over time, making it harder for the infrared light to go thru.
Plain soapy warm water, not hot, and a clean rinse is the way to go.

[Zingsi]

As I am an Amateur and I am not familiar with those
Optical eyes can you do me a favour and show me this on a photo or
Is there a video of cleaning a billvall and box? Thanks so much