BeagleboneBlack Wireless Ubuntu 16.04 PWM produces "RuntimeError: Problem with the cape manager"

I have a beagleboneblack wireless with Ubuntu xenial 16.04. I am trying to use the Adafruit_BBIO library and I am following these instructions : https://learn.adafruit.com/setting-up-io-python-library-on-beaglebone-black/installation-on-ubuntu .

Following the tutorials provided in adafruit’s webpage, I set up some GPIO ports successfully. However, when I try to set up a PWM port, the following runtime error occurs:
https://www.dropbox.com/s/nw8dbwl04rjgums/PMW_cape_manager_runtimeError.png?dl=0

I have found similar threads here: https://github.com/adafruit/adafruit-beaglebone-io-python/issues/136, https://github.com/adafruit/adafruit-beaglebone-io-python/issues/125, https://github.com/adafruit/adafruit-beaglebone-io-python/issues/230. I have tried most of the solutions suggested in these forums, without any luck so far.