Created attachment 166055 [details] XLSX document The document in question is in public access, so I'm attaching it to this bug report.
This doesn't seem to be a bug but the limitation to 1024 columns in LibreOffice while XLSX allows 16384 columns.
Reproduced in Version: 7.1.0.0.alpha1+ Build ID: 03cafc2ab6b1678f82e9a30b6f81e505660ee702 CPU threads: 4; OS: Linux 5.7; UI render: default; VCL: gtk3 Locale: en-US (en_US.UTF-8); UI: en-US Calc: threaded
Same problem with the "ThinkPad, ThinkCentre, ThinkStation, Ideapad and Ideacentre Option Compatibility Matrix" document found on https://support.lenovo.com/do/en/solutions/accs-guide (direct link to the file: https://download.lenovo.com/pccbbs/options_iso/ocm_oct_2021.xlsx ...)
I see nothing wrong with the document when using current master with experimental large sheets enabled, so this is either fixed or dupe of bug #50916 depending on what this is exactly about. *** This bug has been marked as a duplicate of bug 50916 ***
Fwiw, import to 1024 columns raises the warning because some clever mind for the Lenovo document at least formatted entire row 2 starting on sheet 'TP X' (and other) to diagonal cells.. and other formattings applied, similar in the attached document, where cells have borders across an entire row, likely until column 16k.