troff/mm bug with .TC

[Ken Greer]

We've discovered a bug in the use of .TC (table of contents)
with the mm macros.  When a larger than normal font size is used,
the section numbers in TC output sometimes get shifted to the next
line.  For example, a line that should read:

	5. This Is A Section Heading . . . . 2-6

actually comes out as

	5. This Is A Section Heading . . . .  -
	   2-6

We're using ditroff with SVR2 mm macros.
Have any troff experts seen this and know a fix?  Thanx.