I happily joined the Line6 club recently and I am really surprised by the sounds I can get from my HD300 unit, but recently I started to have problems with the switches, nobody changed something in it hardware-wise, everything is factory-like.
It's easier to show you in a video what's the problem so:
I found out that by holding the A switch you enter in a button test mode "P16 TEST MODE", the screen shows "Knob ExtPdl" or "Knob IntPdl" and whatever I push it just jumps back at that and their value keep changing random.
After a few days the problem got worse, now there are some LEDs that light up togheter with others, like the green tremolo light when the orange delay is on, and they sometimes flicker together with the tap LED.
It's just like everything is short circuiting.
I don't know if there is an authorized service in Romania so I could send them the unit.