The original spool shaft for UP! Mini is too short and wide to hold 3rd party filament spool. I have to design a shaft my own in order to restore the peace.
Rotate the object 90ÃÂ° in order that the words 'UP! mini' is horizontally upright to the print platform. You can refer to the screen shot I've uploaded, or just download the UP3 format for the recommended orientation.
If you ignored my instruction and then print the STL file as it is, it'll break sooner or later due to the weight of the filament and its spool, and the way the printer prints the part.