Extras.txt not working on startup (PixHawkPX4 / APM:Copter V3.3.3)


This is the content of extras.txt:
pwm min -c 1234 -p 900
pwm max -c 1234 -p 2100
pwm rate -g 0 -g 2 -r 300

I´ve put the commands in /etc/extras.txt on the SD card, but it doesn´t run at startup. I´ve tried in manual mode and it works (MAVLINK=> module load nsh; nsh start; sh /fs/microsd/etc/extras.txt; pwm info=all changes ok).
I’ve changed the final line in Windows with Notepad++ to Unix. Also, I’ ve tried with gedit and nano in Ubuntu and atom in OS X, but it doesn´t work.

How can I do to make extras.txt run at startup?
Could I change these values in another way to get it to work and remain recorded?