I have the issue where the rear seatbelts would occasionally slip out of the guides. I fixed this by designing a clip that goes over the guide. It easily clips onto the guide and also comes off quite easily when needed.
It's recommended to use PETG to minimise warping and UV degradation. I have the infill and perimeters dialed all the way down (for speed), but it's still quite strong. I have the settings set to a Prusa i3 Mk3s, so you may need to adjust them for your printer.
The author marked this model as their own original creation.