Today I tried to compress and old XLSX file and I got interesting output!!
I think the file had been created by Office 2010. Precomp046 and lower could decompress the file almost without adding any noticable corrections. The size was exactly same as the decompressed XLSX file (by 7-zip); but the output of v047 was bigger. As a result, the 046 file could be compressed better than 047 file.
I tried -brute option too for v047 but also got -d0 and same file size.
Original size: 20,502,859
Precomp046: 98,276,029 , ZIP streams: 12/12, -zl13,14,17 -d0
Precomp047: 98,786,845 , ZIP streams: 12/12, -d0
The story is different with the XLSX saved by Office 2013, for which v047 could find all the streams but v0.46 failed (only found 4 out of 12 streams).
Is it possible to fix this issue for old XLSX files? I can send you the file if you need it.