Characters fail to display

[Fairchild]

At times lower numbered characters do not display, in at least one font set.
The first example below doesn't do as expected.  Deleting the \break as in
the second example or inserting a higher numbered character as in the third
example causes the expected result.

=======================================================
% Does not display characters #04 and #05
\version "2.4.3"
                                                \score{
                                \relative c''{
\override TextScript #'font-name = #"cmb10"
c1^\markup XXX
\break
c1^\markup { \char #04 \char #05 \char #68 \char #69 }
                                }%end relative
                                                }%end score
=======================================================
% Displays all characters
\version "2.4.3"
                                                \score{
                                \relative c''{
\override TextScript #'font-name = #"cmb10"
c1^\markup XXX
c1^\markup { \char #04 \char #05 \char #68 \char #69 }
                                }%end relative
                                                }%end score
=======================================================
% Displays all characters
\version "2.4.3"
                                                \score{
                                \relative c''{
\override TextScript #'font-name = #"cmb10"
c1^\markup { \char #65 "XXX" }
\break
c1^\markup { \char #04 \char #05 \char #68 \char #69 }
                                }%end relative
                                                }%end score
=======================================================