I have recently updated all of our machines to Solidworks 2012 and all work fine except one.  For some reason the toolbox parts keep updating whenever I add a toolbox part of the same type, i.e

When we put a 12mm spring washer into the assembly all is fine, however, when we then want to add some 20mm washers to the same assembly (from the same standard) all of the washers within the assembly are then updated to the latter 20mm size? Any suggestions would be appreciated!

Cheers,

Matt