If there is a Maxima error, e.g., wrong number of
function arguments, an error message is printed and
then another Maxima prompt.
If DEBUGMODE: TRUE is set, then the next Maxima error
yields a break prompt. Then :bt shows not only the
error that caused the break prompt, but also all
previous erroneous function calls. This is confusing.
Apparently a new input loop is started after an error,
instead of restarting the existing one.