I noticed on the original Smartrapcore ALU / XL300, as the Y carriage moved towards the back of the machine the belt teeth began to interlock and started to affect movement in that area. I've redesigned the two rear bearing holders to support the bearing offset and supported from the top and bottom side to reduce the cantilever effect due to belt tensions.
You should need to print 1 of each bearing support, and 4 spacers using the existing parts from the Smartrapcore ALU/XL300 build along with a shorter M8 bolt to act as an axis.
Designed on Onshape at https://cad.onshape.com/documents/bf73580fded0a3ddee7e63c7/w/a4ebe5fdf466658b538d5071/e/d0562b45f4cb7f900afaf7ba
Bearing supports are stronger when printed in ABS or PETG.