Also keep in mind, tools misbehave a lot of the time, it’s just that meshes are unpredictable like that. A lot of time you try it again and it works. Other times you go into edit mode and just clean things up, delete the excess, massage vertices here and there. You can also move your too to do the effecting slightly up or down and it just works, because it might be running straight into a vertex and can be causing issues. Other times you can just use a different tool that accomplishes the same task, just in a different way. But all that to say that these types of errors are common and you just have to do a work around, no matter the software, it happens in Blender in 3D Max in Maya, etc.
