Program automatic interription

Hello friends..

I am using Linuxcnc router having X-Y-Z axis and a spindle.

Apart from little mechanical issues of rack-pinion accuracy, it is working fine.

However, a strange phenomenon happened today. When I was running a G code program in Auto mode, it interrupted i.e stopped executing of its own; there is no such code in the .ngc file(attached). I am more than sure there was no keyboard/ mouse interruption, no power issues. Actually It is the second time happened today and the last time I thought some keyboard or mouse interruption had happened, but now I am quite sure that was not the case. Friends, it is a serious issue. The program started working from the point of interruption when I pressed the program start button in Gmoccapy, but the spindle did not start. I use it for some silver metal design job, so it is risk if I get my job damaged.

I have some classic ladder program for power failure detection and auto-resume program with spindle after power resumes. But I swear, there was no power failure today (and the last time it had happeneded). Also the spindle did not 

What could be the reason ?? Has anyone ever faced such situation??