The upper and lower guide brackets on the Ryobi BS901 are made of a cheap material that resembles aluminum that I think is called "white metal"

Over time this material becomes brittle and breaks or even crumbles.

The replacement parts for this are no longer available. BS90102300

In a pinch I made these that allowed me to work. Not as rugged as the metal ones but this is a pretty mickey mouse bandsaw and they work for what I have thrown at it which is way more than it is supposed to handle.

I printed with supports everywhere. I printed in the orientation shown in the picture. I printed it 100% infil. I used ABS. After removing the support material I had to file out the squares to fit the guide blocks a bit. Figured tight better than loose. I also used an M6 tap to thread the holes for the block screws.

Still working on original set... and if they break I can print more.