Morgan Smith <Morgan.J.Smith@outlook.com> writes:

> Ya I sent a bug report (46332) about this exact same thing happening. 
> And then you fixed it so that it happened much less often. I didn't 
> notice until like a day after we closed that issue. My guess is that 
> there are two unrelated bugs that exhibit the exact same behavior and 
> you already fixed one.

I read that bug report and looked into this. As you said, there were two
bugs exhibiting similar behaviour. One was in ansi-color, fixed by Lars
in that bug report. The other bug, not yet fixed, is with esh-mode.el.
It uses 'insert-before-markers' to insert process output, pushing
forward the marker used by ansi-color.

A reliable reproducer is to open eshell and execute

  sh -c "printf 'NORMAL \033[32m'; sleep 1; printf 'GREEN \033[m\n'"

Please find the attached patch which fixes this.