I have the exact same amp and two KL-203's they all work fine I never got any chatter from the relay on my 503 used as a base station with a 148GTL I have extremely loud audio and my radio on am sits at 2db carrier and swings to 15 watts and on SSB 0 to 18 watts you maybe are not driving it enough and keying up with out talking is bound to cause the relays to bounce on and off and you may not beware of the actual mechanical movement of the mic key up switch will be picked up as audio and you will see the radio and anything inline responding to the audio and the increase of wattage. I did watch your video and my KL-503 does not operate like yours but it's just a tiny glimpse of whats going on there but when talking SSB keep your audio up and when you key up be ready to talk should help.