Lisp values not appearing in command line

I cannot determine what triggers this but the command line has stopped returning values from lisp expressions.

eg.  If I type (setq fred "Hello") I would expect to see "Hello" returned. I am getting nothing.  Similarly if I type !fred I get nothing.  If I restart AutoCAD the problem goes away.  The after some time it happens again.  Has anyone seen this?  Is there a toggle or switch or system variable that I'm not aware of?

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