Headphones are cutting in and out. Trying to determine if it is the cable or the cans?

I’m hoping someone can at least help me trouble shoot to determine the cause for the failure. I have a fostex th900 MK2, purhcased new with the original stock unblanced headphone cable about 3 years ago. For a couple months now, i’ve been noticing that the sound will soemtimes cut in & out on either side intermittenly. If i am perfectly still it seem to improve. Sometimes i can go for an hour with not an issue, but othertimes i have continuoulsy move my head to secure a proper conncetion. ANy thoughts about this? It’s not the amp, i"ve tried two sepeate soruces and have the same problem. The headphones & cable have about 250 hours on them. 80% of the time I use them in a static listening position.

Sounds like a connection or cable issue.  Clean all your connections and see if that helps, and if not try another cable.  
while listening, make small s-turns in the cable to fine the short.
I had this issue with a pair of Oppo phones and one dealer told me the jacks on those phones were minutely undersized, possibly causing problems with some in put jacks.  A new cable solved the problem.  
Thanks all, it was the cable.  Replaced it, problem sovled.