The below rule should add a postag to the existing readings, shouldn’t it? However, it makes existing rules fail, for not finding the proper alternative of the base word. So it looks like the original reading (ZNW:MRV:DE_) is lost.
Who knows what might be going on?
<!-- bezitsvormen -->
<rule name="oma's" id="OMA_S_AUTO">
<pattern>
<marker>
<token postag="ZNW:MRV:DE_" regexp="yes" skip="2">.*s</token>
</marker>
<token postag_regexp="yes" postag="ZNW.*"/>
</pattern>
<disambig action="add"><wd pos="ZNW:BEZ"/></disambig>
</rule>