Helix 6150 Shift questions

[wvcraftsman]

Hello All!
Forgive me if this is in the wrong place.

I bought my son a used American Sportworks Helix 150 ASW. Model: 6150L-29
It has been having some issues when shifting into D or R. I can start it and idle fine forever, as soon as I shift into drive or reverse it dies. Every once in a while it won't die. I can then shift into drive, back to neutral, and then into reverse. Once in reverse, it won't come back to neutral and then it dies.

He loves this thing, but both of us are getting frustrated with it right now.

Any suggestions?

Thanks.