SARA-R410M: Serial Port issues

What is the methodology to remedy the following error:
ERROR: Unable to detect a usable serial port

I am using a program to read data from a sensor using the sensors serial port, while having the modem mounted to a serial port as well.

The sensor’s device path is /dev/ttyUSB0 and the modem /dev/ttyUSB1. However, running the program causes a seg fault, clearly a problem since the modem mounts to a singular serial port. The device paths change after this, which is odd the sensor goes to USB1 and modem to USB2…
The issue here is making the nova usable again I can try to fix the logic in the software of my program.

Looking at the source code on GitHub it iterates through the device paths and find the modem successfull as shown from the -vv output. However, the serial port is unusable? How can I make it usable?