It's very possible that the oil's going away in the front part of the lane and the ball isn't rolling at the right time. I've been struggling bigtime with my Mutant Cell to get more than one game of use out of it (even after a redrilling and about four different surfaces) because it's just so dependent on a high volume of head oil to help it get down the lane. I also see the ball hook less and less as the night goes on.
With my other equipment, I don't see this quite as much on a house shot, but I see it a lot on PBA shots where the heads tend to dry a little quicker. On the Chameleon pattern, for example, I started off with my Cell at 2000 playing around 11 at the arrows to 7 at the breakpoint. After a game or so, I started moving right because the ball just wouldn't pick up as hard in the midlane and wouldn't turn as hard on the backend. I moved four boards right and finally was in the pocket but left back to back flat 10s. I realized that the heads had already dried up so much that the ball was rolling a little too early and burning up energy. I switched to a Gravity Shift with a little surface on it and moved left to play about 13 to 8. The extra head oil from moving left plus the pearl surface to increase skid in the front part of the lane meant the ball actually hooked more and carried much better, and also gave me some miss room to the right where I had burned up a spot.