Multi–face extrude kills command line and toolbar buttons

I ran into a problem trying to do multiple face extrusions where I select individual faces (all aligned, same size, etc), then choose to extrude those to a target. The operation completes, but leaves the command line in its last prompt state, and the toolbar buttons no longer work. I have to pull down the File menu and "Save," then exit and relaunch BricsCAD to get it to reset. It also sometimes disallows panning and rotating with the mouse middle button (+ Shift to rotate).

The cursor responds to crossing or window selections, but won't actually select anything; just the screen looks like it's selecting. I thought at first it was the complexity of the 3D model elements, but eliminated everything but five small stair stringers, and the behavior is the same.

I may have inadvertently caused some setting to switch, but have no idea what or where it could be. I recall being able to do this previously with no bad effects, so perhaps I've broken something.

I've uploaded a test file that exhibits this behavior on my system. Please use with caution, as I don't know what could be lurking behind the scenes, but I've purged, cleaned, audited, etc., etc. as best I can. What I'm trying to do in the file is select individually the five bottom faces of the stringers, and extrude them to the guideline below, a seemingly simple task. As I mentioned, the extrusion works, but then kills all the toolbars/command line, and I have to go to the File menu and Save, then Quit, then relaunch.

Any ideas?

Thanks much in advance!

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