Zico,
Let’s take this to the general list, as MJ suggested.
Shouldn't you be using the -z option for incremental updates?
Nonetheless, that is not the cause of the problem.  The problem does not
occur in fresh installs, it seems to only occur where a data base has been
upgraded from an earlier version.
So does that suggest that a data element has been lost in the upgrade?  If
so, why is the problem only in the OPAC?
It needs a bit of research to identify the exact circumstance.  I won't be
able to do that until after Christmas.