Transmit in Progress Error when sending packets.

I have been receiving “Transmit in Progress” error while trying to uplink a packet to the gateway. This is happening on a particular mdot amongst the 50 mdot’s communicating with the conduit.

Just to give you little background, even though the mdot that is returning the “transmit in progress” error constantly, it had connected successfully to the private lora network at one point and transmitted couple of packets successfully, before getting into the state it is in currently.

Before transmitting any packet I always check the return values of the following two functions mentioned below and also the mdot sleeps for a minute between transmissions.

getNextTxMs()
getIsTransmitting()

So with these checks in place and also with a 1 minute sleep interval between transmissions why would the Send method return a “transmit in progress” error.

Also FYI, we are operating the US915 frequency band

Thanks,
Ajay