Goldtec? If so, you should be able to buy the axle and end caps for 120mm - unfortunately, you do need both, as both parts are different for each OLN dimension. You also have to take the bearings out to replace the axle, which probably means new bearings too.
Yeh, does look like there's something there.. but I can't move it. Haven't really tried yet though...
https://i.imgur.com/QK0hEKC.jpg