I'm not sure if this will relate to your issue, but sometimes I have problems with blocks disappearing after I explode them.
We create spaceplan's with fixtures that we sell. One 4' section of shelving (in the form of a block from our library) may have "x" amount of shelves while the 2 sections beside it may have another amount. So we often explode the blocks (well I usually run a lisp, but sometimes it is just as easy to explode the block). I know some people freak about exploding blocks. We never know how each block should look so we start with a generic and reconfigure it as many times as needed, and sometimes create completely new pieces from parts from other blocks in the drawing.
Sometimes though, when we explode a block (if we are in a shaded view, like conceptual or realistic view .. this never happens in 2D view, but that doens't mean the actual even tisn't taking place**) the block "appears" to disappear .. but in all factuality it is actually still there, it's just hidden. To make it "re-appear" we will simply open another block, then close it and "voila" the missing block, or pieces of the block, reappear.
** now, I mentioned the blocks don't disappear when using 2D view .. but they really do. Even though you can *see* them .. what you are actually seeing is just their "ghost" .. you won't notice the event has occurred until you go to print (unless you open another block between the time it disappeared and the time you print, then you won't know that it happened) and notice part of your drawing is missing.
I've not found anyone (online or via email with Autodesk) that can explain this phenomenon .. even when I've shown them a video of it. But here is a way to check and see if this is happening to you too.
![Autodesk Design & Make Report](https://forums.autodesk.com/t5/image/serverpage/image-id/1350519iCB55845EBFC43016/image-size/large?v=v2&px=999" "Autodesk Design & Make Report")
