Using different USB to RS485 converters

I use 2 kinds of USB to RS485 converters. The 1st one is based with original FT232RL and works well for many days using modbus between a raspberry and a device (Heater system). The 2nd one is based with CH343G and the dozen of first messages are correctly exchanged then some various errors appears(CRC error, ressource unavailable, ...), and the system never re-synchronize the exchanges. The application is the same except the name interface: /dev/ttyUSB0 in the 1st case and /dev/ACMA0 in the 2nd case.
Many thanks
I had crazy experiences while working with such USB to serial converters.
Some brands will work only with certain devices.
But finally figured it out that many of the American brand (Like Trendnet TSU9, Triplite) work flawlessly, where as chinese will have poor success rates.