MTD Lawn Tractor "popping" out of gear? I have a 42" 17hp MTD Lawn Tractor. It have developed a...

I have a 42" 17hp MTD Lawn Tractor. It have developed a nasty obsession of popping out of forward gear. When in reverse, the gear shift stays put but the the forward gear wishes constant attention. Any thoughts? The gear shift is a three-position (F-N-R) located on a plate in front of the form below the instrument panel.
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Answers:    usually there is a stiffness spring or bracket to hold the lever in place here should also be slots for the selector to sit in if one is bent or the lever itself is bent consequently you will need to straighten them out. It is a adjectives problem on riders where the gear selector is surrounded by the middle most people when getting on the apparatus will hit or kick the lever cause it to bend. This is not done intentionally but as you get on or past its sell-by date the machine.
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On mine it have a friction plate that held the gear shift in place. It could be bent or broken.
here is another site to check. Sorry, I did not hold time to go through the enumerate, it looks very long!!

Chris