What you're describing, Krakenfan#69, is a specific behavior of the "RS-232 DF1 Devices" driver, with the "Half Duplex" selection.
It is contrary to logic and experience and I don't really like it.
With the DF1 Polling Master driver, you set the Master node number (often 0) and put the Slave device node numbers in the polling list.
What's possible is that dmelect accidentally configured Hardware Handshaking, which means he'll have to set up a driver that supports it and use a cable that supports it.