Reverse question

reverse

Sounds like you just need to adjust that cable. The lever on the outside moves that counter gear in and out. That gear has pins for lack of a better name that engages another gear that is meshed with the chain. If that movable gear isn't moved properly it will not go into gear right. I had one with missing teeth on the idler gear but it sounds like you have inspected everything so it may just be cable adjustment. Obviously make sure it has enough oil too. You have to be at a complete stop when you change those gears because they don't have any syncros and the pins are cut square. Also that lever just applies pressure to a spring to move that gear so it may need to turn up to half a turn before the pins line up and it engages. Make sure chain is adjusted too.