Hi rc-mike,

There are a couple of washers inside the 8U, but they are on the underside of the switches, these would never come loose inside the transmitter unless a switch has broken.
The washer in the picture does not look like anything that would have come from our factory.
If you would like to send the radio in, we will be happy to check it out for you to make see what type of damage this may have caused internally.

If you purchased this second hand, you may want to check with the last owner to see if they have any idea of what this washer may be.

I hope you find this information helpful. You can also reach our Futaba support technical team at 217-398-8970, or via fax at 217-398-7721.

Sincerely,
Krysta
Lead Futaba Customer Service and Programming Technician
Also you may want to check our Website at (http://www.futaba-rc.com)