Ok, researched OLE property sets and started work on reading and writing them. It should not be bad, although I was surprised that both libole2 and POI had some rather significant confusion here. However, adding this did not solve the warning from MS Excel so I was forced to merge in patches 1 at a time from 1.1.5 to present to see where the exported file went wrong. It turned out to be the selection exporter. The old version just hard coded A1 the new version tried to be correct, and ended up specifying the selected pane as #0. Excel did not like that. It wants the pane to be #3 if there are no splits.
Once that was found it was time to release 1.1.8 so that the pango code can get some testing.