You mention “putting a quarter under the clock” Will it run with the quarter under the clock? If so, then the clock is probably out of beat, or the pendulum is bumping against something. Does the clock have good motion with the pendulum “plenty of swing”? Does it have a nice even tick-tock, like a metronome, or is it uneven “tik – t o c k” sound. If this is the problem, the beat needs adjusted by moving the crutch/verge adjustment until is the beat is even. These might well be the problem.