Interesting you bring up this topic, I have a 20ga sterlingworth that does the same thing your talking about. The trip works exactly as it is suppose to as long as you hold it to the full open position and move the barrels to the open position. I have several graded Fox's and have never found this to be a problem, but all of them have the deely type forearm latch. I attribute the sterlingworth issue to the spring loaded snap-off forearm which holds some pressure on the barrels to action and because of this you need to be more aware of opening the barrels farther before releasing the opening lever.
This is just what I've found with my gun.
