I'm controlling Brennenstuhl RC CE1 4003 power plugs with 433 Utils running on a Raspberry Pi.
To get the code working for this specific plugs, I had to change the order of these two lines in codesend.cpp:

if (protocol != 0) mySwitch.setProtocol(protocol);
if (pulseLength != 0) mySwitch.setPulseLength(pulseLength);

I'm not sure exactly why this has to be done, but I could not get the Brennenstuhl power plugs working without the change.
I made the changes after reading this thread, which documents some troubleshooting with the Brennenstuhl plugs (unfortunately in German): https://forum.arduino.cc/index.php?topic=513836.0

The adapted code is running without problems for years now. I just saw my notes from back then and decided to open an issue and pull request. Thank you for this awesome library, it makes home automation a lot easier :D