A common problem during our OOXML import is that there are several different OOXML dialects: OOXML transitional, OOXML strict and the not specified version written by MSO 2007. The MSO 2007 version is mostly identical to OOXML transitional with the small but nasty exception that they have some differences in the default values. Recently I got a document from a Collabora customer using MSO 2007 exhibiting some bugs related to that.
A few days ago I finally managed to bring support for handling the differences between the OOXML dialect written by MSO 2007 and the one in the specification to LibreOffice. This is an important step forward for our OOXML chart import as that code was written against the MSO 2007 version and more and more documents are generated by newer MSO versions. In recent years we have changed quite a few of the default values in the code to handle OOXML specification conforming documents correctly. Sadly this introduced a number of regressions for the handling of MSO 2007 documents.
With  and  we are now able to recognize files that have been created by MSO 2007 and are able to use different default values. Currently this is only used for the flag that decides if the chart title is deleted but more cases might be fixed in the future.