When I open a file in ACAD2013/ACAD2013LT I can't see some XREFs created in ACAD2012LT. XREF command cannot resove it either. It will show path correctly.I would hate to downgrade all stations to 2012 just to resolve that.
Is A.7 the "main" file? it's in 2010 format according to R2013. It was also missing the XR-Sections xref, which when added, makes your section appeat. The other XR-Sections2 file is there already. See screenshots attached.
I do notice you have a few XREFs in as Overlay, and others as Attachments in the XREF: may I ask why the variety?
Both of your XREF files report "AEC" content and they both appear to be in R2007 format: are these from someone outside your office using AutoCAD Architecture? R2013 and LT2013 has some issues displaying AEC content that's not quite resolved yet: ensure your 2013 seats are fully updated and patched and have any required Object Enablers installed. if you don't need the AEC content, explode these files using -EXPORTTOAUTOCAD command (there is a dash in the name) down to R2000 format then save back up to your office current format.
Witrhout being too familiar with your files and project, I'm really not seeing any issues with 2010 format files being Xrefed, they appear to be all here in your top file in 2013.