FT8 PROBLEM AUDIO TX - FLEX 6600 REMOTE

Hello. There is a problem with my 6600. When it was at home and I was working on FT 8 using WSJTX everything was OK. When I went to the country as a remote station and I work via SMARTLINK and WSJT the sound transmitted by TX is very wide on the screen and very strongly jerks the modulation. On RX everything is OK. The signal is clear and stable. There are no interruptions. You can also see power fluctuations. Restarts and restarts of FLEX and PC do nothing. I guess the problem may be low temperature because the radio is standing in conditions of about 8 degrees Celsius. Currently I do not have a computer in the second qth to connect to Flex via the local network and check if the problem also occurs. I have a maximum ping to the radio of 50 ms. So it is probably not a network problem. When connecting Mestro remotely I see that on SSB the sound effect is the same. Heavily distorted audio signal. All levels are set correctly. As I wrote above, when he was home, everything was OK. I'm really starting to wonder if he's not too cold. If you know anything about this, someone had a similar problem, please help. Best regards, JACEK SQ5AAG