Just got the FBV 3 two days ago. It switches through tones fine with bank switches A â€“D. I have not yet checked out the 5 FS buttons. I have found 2 problems. The Function button changes the amp to function mode but does no illuminate the button the FBV 3 will not edit parameter. Second, pressing the tuner only shows the tuner on the amp and not the FBV 3. I have found the documentation and line 6 online support very superficial and will be calling support.
One thing to note. If you use the bank up and down buttons, it must be followed by a bank A - D press. So if the amp is using tone in 01 A and you only press the down bank, it will flash 02 B but if you don't quickly press A - D, the tone will go back to 01 A. If after you hit the down button and then hit B, the tone will change to 02 B. Likewise if you to hit D, it would switch to 02 D.