[Icom] IC 746 tuner

[Guillermo]

	Hello, a friend of mine owns a 746; he uses internal tuner to feed a
multiband dipole. In a few bands, we noted that even if SWR (as seen in
746's SWR meter) is not more than 1.2 (full carrier out, RTTY mode),
when he speaks in SSB mode, TUNE label starts to blink, and after a few
seconds, tuner is disengaged. It is like that at a higher peak output
(which?, because at RTTY we have full power out, peak SSB can't exceed
this) tuner still detects standing waves and try to re-tune, with no
success.
Later we found that also at RTTY, tuner has the same behavior after a
few seconds key down.
Any hint?

Thank you in advance
Best regards
Guillermo - LU8EYW.