murrayr,

The Shortboard MK II is compatible with the Flextone III series. I was also unable to duplicate the problems you describe.

There could be a problem with either the Shortboard or the amp, but will be tough tell unless you try either one with a different amp or pedal.

Also, make sure to check that the pins in the RJ45 jack of the amp or pedal are not bent.

You can also try resetting the amp to see if it will fix anything. Keep in mind that this will reset all presets to factory settings:

Press and hold the A and D channel buttons on the amp while you turn it on.

If the problem persists, you will need to take either to an authorized service center to take a look:

http://line6.com/service_centers/

Regards,

Line6Hugo