Mozilla/5.0 (Windows NT 6.1; rv:45.0) Gecko/20100101 Thunderbird/45.1.0
As it has been kindly explained to you on the former thread you opened,
and in this one, you have either a driver or a port problem.
Most likely your code is polling at regular intervals and what you see
as varying delay is the phase difference of your ping frequency and your
poll frequency "signals".
Other possibility is that you are extracting only one frame out of the
controller, as we've seen countless times here in the list, that you
should search for others having had this very same problem and having
been solved.