Arduino 101 and Serial Monitor

Recently switched from using a MEGA 2650 to the 101. Ran into issues uploading. USB 3 ports don't work. USB 2 ports do.

Code for EZO-Flow shield worked fine on MEGA. But Serial Monitor would not send any commands to device.

Used the MEGA to set device for continuous output and reconnected to 101. 101 Serial Monitor was able to read output. But could not send any commands. Output also very susceptible to noise. Touching the device or wires would introduce garbage characters into Serial Monitor.

I've tried a couple of different baud rates. So far, same results.

Any thoughts or suggestions on what I might try to get Serial Monitor communications working?

Is that a proper stackable shield or the sensor board attached by wires / jumpers ?

A decent link to it would be nice.

Also the sketch being used as the two boards you mention are totally different architecture.