Our home has several room closets with three mirror sliding doors. In one room, the bottom door roller was always getting out of track and jamming once in a while.

I find out one bottom retainer was missing  and another was broken. I couldn't find the replacement part from the original supplier, so I decided to draw it in Fusion 360 and print it. 

I reinforced it and adapted it to 3d printing. There is not much force involve  so PLA is fine.

I have also included the original drawing in case you want to adapt it to your own sliding door model.