This is very user-specific but I'll post it anyway, maybe it could be useful for other people facing the same issues.
So, I have a Monome which was built by a friend of mine. It works smoothly with all Max/msp apps such as MLR, AprShift and etc, but when it comes to Pd all the data gets messy.
What happens is that "led_row" and "led_col" messages sent by Puredata returns weird things in Monome. Turns out that some good fellas at the Monome forum told me that probably the logic board is flipped. Since I'm not by any means opening my Monome ('cause if I ruin it I won't be able to give my friend to fix it) I created a rather simple abstraction that "translates" the messages in a way that the weird one can understand and interpret the way they have to behave.
So now is just a matter of adding this tiny abstraction right after the regular messages and works smoothly.
Maybe the code is not the greatest thing in the world but after all it was a good exercise.
So here it goes if someone faces the same issue one day