Toolbox to part replacement problem

Hello, I recently saved a copy of a screw from the toolbox as a different part with a new name in a different folder, I had to do this because I couldn't find the exact screw I needed so I modified some measurements and added specific configurations to this copied part. When I add that new part to an assembly everything seems fine, then I save the assembly and before opening it again I check that it references the screw that i just created, everything ok so far. But when it opens the assembly it has replaced the screw i had added with a more less similar screw from the solidworks toolbox, how can I prevent this from happening and make the reference to my screw stay? It happens every time I try to open that assembly no matter how many times I save it.
Thanks a lot!

This is how it looks like when I save it

This is how it looks like when I open it again

SolidworksToolbox