RFD Radio Raw Data troubles

I have a couple RFD900x modems that are having trouble connecting reliability. I’m using them to connect my laptop to the data stream coming from the remote instrument. The instrument is connected to the RFD900x through an RS232 interface board. Baud rate is 128k from the instrument to the Radio Modem. The air rate between the modems is 250k. Frequency range is 915 to 919. The laptop modem is set to the same but the baud rate to the laptop is 256k. To control the instrument through the modems there are single character commands that get sent.

My problem is that when the instrument and modem are powered on after a battery change, there is often a ton of dropped data. With the instrument remaining powered, we have to cycle the modem on and off until a solid connection is made. Sometimes it only takes one cycle, sometimes 15. Does anyone know why this is the case?