I'm thinking that either the VX-6 keypad is extremely sensitive or you are inadvertently sending tones more than once. The fact that it works well with Supermon shows it's likely a keypad issue. I have sent tones from 3 different Yaesu FT60s without issue.
<X><
73 75 Mark????
Port Colborne, Ontario,?CANADA
??Echolink Node# 736666
LIFE has an EXPIRY date. No Trees were harmed in creating this message, however, many electrons were inconvenienced.
Mark VE3JMR