Scag Walkbehind Belt Drive Transmission sleeve shifting to the left

Recently I noticed that WB was making a noise with the drivebelt spring tensioners. They sounded like they were rubbing against something. Here the belt-drive unit had shifted to the left rubbing against the spring tensioners. Investigating it further, I can easily move the move the transmission sleeve/axel from left to right with just my finger. The other side of the transmission is fine. Attached are photos where you can see how much play there is by gap next to the tranny.

I don't...

Scag Walkbehind Belt Drive Transmission sleeve shifting to the left