Hantek 5062 Bug Triggering falling edge ?

[infosquadsn]

I am trying to trigger a Reset active low pulse from a functional Intel based mainboard with my Hantek DSO5062BMV. I set my scope to take a single sequence with falling edge trigger and sometimes i can get the 4ms (aprox) pulse but in most of my attemps my scope just cant see the falling edge.
Sometimes i can get the pulse few times in a row, and sometimes i try 10 or 20 times and nothing happen.

I tried with many ammounts of memory depth, with persistence and nothing works.

Am i doing something wrong or it could be some bug with my scope ?

I will attach a screenshoot from the mentioned pulse.  Thanks in advance.