Always check the incoming power first, including receptacle, plug, cord, and attachment. Then, Make sure you've got consistent 120 to the timer. Using your meter on the voltage scale, clip the leads on to the incoming power terminal on the timer and the main neutral lug. then start a cycle, remember you'll have 120 esposed in there, so watch where you stick your finners. Watch for an intermittent drop in voltage, if/when you see it start working toward the power supply from where you've id'd the problem to be. On that unit there is a lid switch and I think a out of balance switch ahead of the timer. Don't remember what else. There may be a schematic either inside the top cover where you gain access to the timer, inside the back cover of the unit where you'd get access to the drum or in your book. That should help track what is on the line side of the timer. Also, make sure that the neutral, aka white wire, is making good connection to the timer, If that is loose somewhere it'll cause what you're seeing.
happy hunting,
jj