Class 87 Won’t Go Into Reverse

The reverser handle will only sit in the forward position or the off position on the 87, even when I try and move the handle by interacting with it instead of using the D-pad

 

Near the reverser there is a button, I believe it has a label of reverse lock or similar, press this and then it should be able to be moved into reverse.

 

Yep exactly this

 

Thank you

 

I have this issue but with every other diesel just worse. It always (except for the 52, the only one that properly functions) says "Engine Only" in the off position and refuses to work.