Panasonic has just released a free firmware update for its S1 and S1H full format cameras that addresses flicker during V-Log recording. In our tests we haven't noticed any problems with flicker in V-Log mode but we have heard from users whose cameras were affected.
As usual, the firmware update including update instructions for the Panasonic S1 and S1H is available as a free download
here on the Panasonic pages.