In my opinion the whole program is a bug. :realmad:
You need to make sure what you are doing after you make the selection.
Doing what you describe above is equivalent of just selecting a bunch of stuff in Acad.
Sounds like you are hitting the erase or delete key. Hence you get the same results as if you were to then hit Erase in Acad.
Keep struggling through the thing. Eventually you will get to where you don't know whether to shoot yourself, the programmers who made it, the company that forces you to use it, or the guy that keeps giving you the Craprostation work, or all of the above.