Toyota Repair: Sienna Starter engagement, place rest, toyota sienna

Question
I have a 2002 Toyota Sienna, 70,000 miles -- The starter at times will not engage, sounds like starter gear is hitting flywheel. I had the flywheel checked twice, by qualified mechanics, teeth ok, not a mark any place. Rest of starting system also checked. Also,no marks on starter. Tried used starter, same thing. Talked to Toyota mechanics, said they never heard of a problem like this. It can go 6 months, or happen twice in a day. No one can find the problem . HELP!!!.. Thankyou very much

Answer
There is either a bad spot on the ring gear of the flywheel which they have not been able to find or the starter is causing the problem, I agree that this seems very unusual but it has to be one or the other, try replacing the starter with a remanufactured toyota starter and if that doesn't help the only thing left is to replace the flywheel.