Thanks @kseniia.suzdaltseva for your response. I confirm that our modules has 28.4 firmware version. We are sure that the Emlid Reach firmware does not work properly, we have a proof of this in the uploaded video (Emlid Reach RF input correction hack - YouTube) and the same issue is mentioned in post: HC-12 radio with reach.
To clarify, somehow firmware does not work properly using RF connectivity. We don’t understand why we were able to make it work (not directly only with the mentioned hack) in transmission rate 115200 bauds and not any other?
Btw, when we are listening from a PC through a serial terminal. connected at transmission rate 115200 bauds, and the start the Emlid Reach module, we are able see a prompt terminal for login to the Emlid Reach. Could it this be related with the issue somehow?
