What kind of cable is it? It's recommended to stay under 150' so should still be fine at 125' assuming good cable. If you are using rg59 instead of rg6 then that would be your issue.
But as with anything electrical the longer the cable the higher the voltage drop due to resistance.
Is this a 'Dish Outdoors' setup? Or a residential type install?
What dish? What receiver?
For a Dish Outdoors type install, ie a Tailgater, Playmaker, etc...in general.... the shorter the coax the better. We tell customers that we really want that coax to be 50 feet or less and no barrel connections in the mix...if possible.
If it's a residential or 'permanent' Dish setup, can you give more info or some pics please?
Is a satellite finder not supposed to be used at the dish with the shortest possible cable run?
Also. DBS lnb's are particularly power hungry and is why using a multi with an FTA receiver can burn the tuner out.