i really hope you will find the source of the problem.
as for the free ram monitoring, there is a function example in the adafruit article, which describes how to monitor the remaining free ram. maybe it could be useful. i used once.
also, another thing (off topic), not just for you…
for a much transparent / better / easier coding, i recommend to use tabs in the arduino ide. as i observed, very few people know how to use properly the arduino ide, and this functionality is not well documented. as limited and dumb as is the official ide, but one can be more productive using these tabs!
the basic idea is, that you should write EVERY function in a separate tab. (for convention, i always use the exactly same name for the function and for the tab name. this is how i learned in object oriented php 
could be awkward in the beginning, but very soon one will realise how much easier it is to manage a large project, using tabs. everything is well explained here, please read: https://liudr.wordpress.com/2011/02/16/using-tabs-in-arduino-ide/