Child rows are not compatible with fixedHeader

[in-op]

If you have a table that has both a fixedHeader and expandable child rows with .child(), then when you expand the child row the fixedHeader doesn't seem to re-calculate the table height and will end prematurely if you scroll down.

You are absolutely correct. What you need to do at the moment is call the fixedHeader.adjust() method just after you show the child row. We should perhaps have DataTables trigger an event on child row show / hide and have FixedHeader listen for that automatically...