attached magnetically, So you can undock? However you say that they are still together buy there magnetic forces so they have undocked. you just need to thrust away. You could also try swiveling it and spinning it so it's no longer effected, then ditch it if you don't need. Also you say that your game crashes when the part lands, is it large or, more importantly does it have a large part count? then that could be why it crashes. i doubt it's to do with your mods as i know from past experiences crashing things with large part count doesn't help the computers mood.