Hi Jonathan
Yes I was afraid for it.
The bolt of the reel is extremely stupid designed.
It is like it is.
But when ordering a new one have a look at one where the lip is a little longer. So you can mount it much easier. They exist as I have found out my self too.
And maybe the belt itself in the color you like at most.
Do have a look again at the article mentioned earlier.

Seat belt inertia locked

Think also about the idea to modify the tray for a next time. Not only for renewing but maintain the reel and the belt clean once in a while.

One ant does not know anything, 2000 are a super-intelligent brain. That's like this helpful forum.