3D rotation with snap

Hi guys! I'm currently working on a small project in Unity on which I need to perform a 3D rotation on a cube with a mouse drag. The thing is that, while I'm currently able to perform a rotation (only in two axis doe the fact that currently I'm only using the mouse position without any concern of the cube relative rotation to the world) and snap it to the closest Up-Front axis, I cant work around the problem of, if my assumption is right, the gimbal lock when I perform a rotation that will presumably end on the complete rotation. This might sound a little bit confusing, so I will give you a link to the repository with the scene so you can check that unexpected behavior. If anybody could help me with this it will be awesome. Thanks in advance!!!

https://bitbucket.org/Burgrokash/rotatortest/src/master/ Bitbucket

Sorry about my English, it's a little bit clunky