That's never been an issue for me, in fact I avoid digital servos because they consume more power. I agree that a nice high quality digital servo will out perform many(most) analog ones but for offroad & my level of racing(local clubs), I never found an advantage in using them. They normally cost more, some brands have reliability issues & they all run down your RX pack faster.

Bagged, I missed that you had replaced the switch, so that's probably not your issue. Given the stuff you have replaced, the battery is your most likely bet. Also hrdcoreglf gave you some good tips as well. I always keep old scraps of foam around to jam into my radio box to keep stuff in place.