@felmue Hey felmue, I've managed to sort out my issue. It wasn't a power thing.
I've been using PlatformIO to do my work as I'm trying to start using VSC for a number of tasks. I ended up going back to the Arduino IDE and surprise surprise the above code compiled and worked ok. So Iwent back and started looking at how I was trying to use the library in PlatformIO. Because the M5Tough library didn't appear in the usual library list, I had just copied the files in the GIT repo under the src folder into my VSC project src folder. It turns out that this works ok for some examples, but not the buttons one (I assuming it tries to reach a header file that it couldn't locate for these ones or something.
Anyway, I found out how to add a third part library into PIO using CLI, started a new Tough project, and now the code works well. So in the end the problem was my lack of understanding (again!) but at least now I've learnt how PIO goes together.
Thanks for the suggestions and your time, I sure you'll get another chance to try and help me in the future :)
galeap.