Kenwood TS-430s intermittent transmission

My TS-430S  transmits 100 Watts on FM in any band in horizontal and vertical positions. Also, using the other modes (cw-am-ssb) has the same output in the vertical position but this output lowers and or finally becomes zero trying to turn the transceiver slowly (by two hands) from the vertical position to the horizontal one.

I think the above two cases have a difference in the IF unit which already has been resoldered in the past.
It doesn't seem to be a relay as the trancceiver operates normally in FM mode.

Please any ideas or suggestions.

Thank you