anyone ever experience this?
I've experienced a situation in which a user cannot undo any operations because the call-back function of a Command Reactor is being evaluated on the :vlr-commandwillstart event as the Undo command is invoked, and is performing an operation which is then immediately undone by the Undo command, hence not actually undoing anything in the drawing.
Needless to say, the simple solution to the above scenario is to check the reactor data supplied to the call-back function for the Undo command and don't act on this condition.