In 21.2.36, the help strings of `balloon-help-mode' are truncated, i.e.
there is a right pointing arrow instead of the last character. Same
story for e.g. the string which should be displayed according to
More oddly, if you press [End] while the help message is displayed, it
disappears and if you move the mouse pointer on to another toolbar icon,
the end of the help string is shown - with the left side being
truncated. [Home] brings you back to the string's beginning.
Sorry, no screenshot. I can't move the mouse pointer, otherwise the
balloon help window disappears ... ;-)