Product review (5 stars): This solved Both my problems.  Read on...
My symptoms were two UNRELATED problems, caused by the single timer.
Problem 1-- Sometimes no heat.
Problem 2-- Timer would fail to advance through the "cool down" cycle, and just stop.
I took the old timer apart.  I found two problems in the old timer.  First--The contacts that power the electric heating element were burned and had carbon deposits... the carbon would sometimes act like an insulator, and no power was going to the heater element.  Second--The plastic "cam" (one of the many cams) was worn, and would not make the metal contacts inside "connect" at the end of the cycle, because that portion of the "cam" is smaller by design. Therefore the clock would stop progressing.
Oh, and yeah, the new timer works perfectly.