problem following removal of keyboard (VAXstation 2000)

[Brain in Neutral]

Anyone seen this one?

I had the DEC field service engineer come in to replace the keyboard
on my VAXstation 2000 (Ultrix 2.2 Worksystem V1.1, running X) because
it was too bouncy (e.g., you type abc and get abbc).  After unplugging
the old keyboard and plugging in the new, the return key worked only
*every other* time.  After logging out (all windows disappear and new
login window appears) the return key worked again.  Unplugging and
plugging in the *same* keyboard while logged in produced the same
effect.  Again, logging out solved the problem.  A test with a third
keyboard produced the same result, so clearly this is not a keyboard
hardware problem.

What's going on?  The engineer said that this didn't occur when he
swapped a keyboard on a running VMS VS2000.