[Elecraft] [K3] SSB TX modulation heard in phones

[Richard]

Duri, HB9DOC, has an issue with his K3: when TXing on SSB, he hears his 
own voice in the phones, but only if the microphone is plugged into the 
rear connector, not when using the front panel one.
And it can’t be RF feedback since the sound is not distorted at all.
MON is set to 0
MIC+LIN is OFF
He is also using the P3.
We both searched the manual but no joy.
Suggestions will be much appreciated.

73
Richard - HB9ANM