manpages transform and tables: CALS versus HTML markup

I've just converted a bunch of DocBook tables from CALS markup to HTML markup. I then find that the manpage transform omits them, or rather, all I get in the output is:

.TS
allbox tab(:);
.
.TE

A diff between the output produced for the CALS versus HTML table looks like this:

 .TS
 allbox tab(:);
-l l s s
-l l l s.
-T{
-\fBCommand\-Line Format\fR
-T}:T{
-\-\-directory dir_path, \-d dir_path
-T}
-T{
-\fBPermitted Values\fR
-T}:T{
-\fBType\fR
-T}:T{
-string
-T}
+.
 .TE

Our setup has a bunch of prepreprocessing, so it's possible the trouble lies there, although the DocBook that we end up shoving into the manpages transform *does* contain the table source.

So, quick question: Is the manpages transform known to have issues with HTML-markup tables, or should I continue to look elsewhere for the source of the problem?

I can provide more information if necesssary; I'm just making a preliminary inquiry for now. Thanks.