I am in octave-mode running an inferior octave shell. Now I mark a region and issue 'octave-send-region'. As expected, all commands are executed and echoed in the shell buffer, and highlighting is finally cleared.
After a couple of more region-sending, however, it stops to work: The corresponding commands are still executed, but the highlighting fails to clear (it can be cleared using Ctrl-g).
I see this behavior now for at least a couple of years, before that it was ok.