Валенок ты утомил

Several MODBUS transactions can be activated simultaneously on the same TCP
Connection.
Remark: If this is done then the MODBUS transaction identifier must be used to
uniquely identify the matching requests and responses.
The transaction identifier is used to associate the future response with the request.
So, at a time, on a TCP connection, this identifier must be unique. There are
several manners to use the transaction identifier:
- For example, it can be used as a simple "TCP sequence number" with a
counter which is incremented at each request.
- It can also be judiciously used as a smart index or pointer to identify a
transaction context in order to memorize the current remote server and the
pending MODBUS request.
Переводи пожалуйста сам, если никто не делает уникальный идентификатор, как того требует протокол как раз и есть БАГ. Удачи.

да, ссылка https://modbus.org/docs/Modbus_Messa...uide_V1_0b.pdf