RS232 (FT232R) - Different TX voltages with the same adapter under Windows and Linux

I have a USB to RS232 adapter cable (FT232R) that I use with Windows and Linux. Therefore I use a Python script with pyserial. Under Windows, the lowest voltage during a data transfer is -6.2V and the highest voltage is 6.2V on the TX line. Communication with a connected device works perfectly here. Under Linux I send exactly the same data (same python code), but the TX voltage is shifted upwards. The lowest voltage is -0.8V and the highest voltage is 11.8V. The communication fails here. When I measure over a 10k resistor the voltage is positive at the beginning and drops during transmission under Linux (see images). How can I adjust the voltage under Linux (Ubuntu)? The adapter cable is from W&T (https://wut.de/e-38011-ww-dade-000.php) . Under Linux the adapter is recognized as "Ltd FT232 Serial (UART) IC". Images can be found here: https://imgur.com/a/lB78S4a