Emacs ignores keyboard, mouse input after returning from ediff

[Stephen Leake]

I'm getting a very weird symptom; often after closing an ediff session,
Emacs ignores keyboard and mouse input; I have to kill it from the
console.

I'm running a recent master build in Debian testing in a VMWare virtual
machine on a Windows 10 laptop.

Has anyone else seen this?

It's not the VM switching to the host; M-tab switches to other Debian
windows, and the keyboard works there. It's like Emacs has stopped
processing input events.

Any hints on debugging?
-- 
-- Stephe