Re: Did something change with respect to Emacs idle loop:

[Richard Stallman]

    Here, "touch the keyboard" == pressing even a prefix key -- I
    think this is equivalent to emacs receiving a kbd event? For
    instance, just touch the control  or alt key does not get it
    unwedged, pressing ctrl-x (or other prefix keys) gets it unwedged.

To get to the bottom of this, I suggest running Emacs under GDB.
When it gets to this situation, you can then investigate what
Emacs is actually doing.

This is assuming that rebuilding with the recompiled Lisp files shows
the problem has not been fixed yet.