A common issue with the 450 and 452 seat belts is that they seem to get tangled up with use. This is annoying and takes a few minutes to resolve so let's fix that.
Tools required: 17mm socket
This is what the seatbelt looks like when tangled up...
...and this is the hex bolt we are going to undo in order to untangle the belt.
Using your 17mm socket, undo the bolt and then remove from the seat.
Don't remove the bolt from the seatbelt itself as there is a washer on the other side that needs to stay there.
At this point, you can straighten out the belt. You may need to slip the belt out of the upper guide to do this properly but make sure it goes back in. Make sure that when done, the bottom bolt goes back into the seat and is done up as tightly as possible. It should look like this when done.
This is what it should look like when attached into the seatbelt clip.