Hi Dave,
I'm not able to duplicate this problem with DocBook tables in
epub3/chunk.xsl in 1.78.0. However, several templates for DocBook elements
use HTML tables for page layout. Can you identify which input elements are
producing the invalid HTML5 table output?
Likewise with mediaobject. When I process a mediaobject that contains an
imagedata element with align="center", the output I see is: