[Amps] Acom 2000A Question

[Herbert Schoenbohm]

I have an Aocom 200A and like it very much.  However, I noticed an unusual
problem that now occurs. The amplifier works well on all bands except 20
meters. On 20 meters I get an error message with the warning to reduce
power.  The unit malfunctions with any drive level; over 10 watts.  My load
is 1.1 to 1.  Do you have any suggestions on how I can further check this
problem?
Or...do you have an email for the manufacturer in Bulgaria?
Herb Schoenbohm, KV4FZ