Sounds to me like the reverse servo was constantly pushing on the shift lever, it takes a lot to break it.. That shouldn't be too hard to fix though. I don't think I would run it with it broken though as the reverse servo linkage keeps spring pressure on that lever to keep it in gear. Think of it like a shifter on your car that you have to hold into gear, it won't stay on it's own..

Hopefully you get it fixed quick and are back out thrashing again soon.