Re: input-pending-p

[Richard Stallman]

    I shall try to find out more; however, I am not very experienced at
    using gdb.  If you can give me some clues on how to proceed I shall
    see what I can find out.

Have you tried stopping Emacs using GDB when it is the "turn" for
the failure to happen, inserting a breakpoint at get_input_pending,
and stepping thru to see what happens?

If mouse motion gets in the way, it might help if you put the window
manager in click-to-focus mode and define keyboard commands to change
focus.  That way you could go to GDB without touching the mouse.

Other than that, I don't see how to give any more advice until you say
what obstacle you have encountered.