Kenmore Series 90 elite washer -sometimes- doesn't drain in last Spin cycle paired to dryer model number 76912692

[NeedHelp]

   Lately my wife is finding that after a completed cycle there is still (clean) water in the bin with the clothes. If she tries to turn the control back around to the start of the last spin cycle she can sometimes get it to go through with the last part of the cycle including draining. 

   Do you think replacement of the timer/control is likely called for? It doesn't seem mechanical because it sometimes does exactly what it is supposed to do and can often be made to complete the full cycle when it doesn't. 

   Unit is probably 20 years old but wife prefers repair attempts because of all the stories about new washing machines being harder to repair, more likely to break down. 

   I gave the washer model because all the grime or wear is making no number visible on the washer where I look. I could take apart further to see if I can find the number but figured the problem description and the paired dryer model number would suffice for now. 

   Appreciate any wisdom.

NeedHelp in Boston

[16345Ed]

Could be as simple as drain siphoning. 
 

What’s the drain set up?

[NeedHelp]

Hose out the back, up a couple of feet to PVC pipe draining down. Doesn't seem to keep it from working when she spins the dial back to "spin" a couple of times. Then it completes draining and spinning. 

[16345Ed]

54 minutes ago, NeedHelp said:

Hose out the back, up a couple of feet to PVC pipe draining down. Doesn't seem to keep it from working when she spins the dial back to "spin" a couple of times. Then it completes draining and spinning. 

If stand pipe is draining too slow you can get siphoning. Just FYI 

[NeedHelp]

It seemed to be clear when I did a little roto rooter on it but I'll keep it in mind. Like most intermittent problems it will be difficult to troubleshoot because the last two times it worked just fine (before doing anything). Tomorrow it may be crankier. So, it's hard to figure out what's wrong and what attempts make it right. 

   Thanks for the possible problem to look for.