Bosch SHU 4000 Diswasher timer not advancing P/N 264177

[markcm]

Our amazing bosch SHU4000 dishwasher which has provided us with thousands of washes over 20 years without missing a beat finally gave us our first issue. The timer stuck in several positions leaving the machine running for hours on end until we manually moved it forward.

The machine is absolutely amazing and we would love to keep it going. I am hoping to find a used working timer or a DIY to repair this one. If all else fails I see that ApplianceTimers dot com  (LINK) offers a repair service and I have used them before with good results. I'm pretty handy, good with mechanical and electrical and have done some other appliance DIY such as finding cold solder joints on our Thermador Timer and repairing it; I'm hoping to learn what the failure mode is in these timers and maybe repair it myself. 

From what I have found, the OE part number for this timer is 264177, interchangeable part numbers are reported as: 
467078
AP2804275
BSH 264177
PS1443427
PT8412825
AH3448278
EA3448278
PS3448278

Any tips are appreciated.