MH-10 Bluetooth modules not responding to AT commands

I have 5 identical HM-10 Bluetooth modules.

My HM-10 modules

One of them works great. I plug it into my breadboard and I can talk to it with AT commands.

Module plugged in

Code results

But the other four modules don't respond to commands. The red LED blinks like it is searching for a bluetooth connection but when I try to send any command I get no response.

results bad

The Arduino sketch I'm using is called SerialIn_SerialOut_HM-10_01 which can be found On this site.

I don't think I have an 80% hardware failure rate here; that would be crazy, right? Any other ideas about what I can do to regain control of these?

PaulCollett:
I don't think I have an 80% hardware failure rate here; that would be crazy, right?

Indeed it is, but, on the information you have given, that is nonetheless a reasonable conclusion. I think you need to elaborate on what you have done to the one that works that makes it different
from the ones that don't. It may be just decent wiring or a good spot on a slack breadboard.