Created attachment 199074 [details] custom frozen spreadsheet.xlsx: hand-modified to force wrong topLeftCell The problem occurs during export, if the sheet has a frozen view and somehow the bottom-right pane is showing some of the frozen range. In this case, it was writing the topLeftCell as a cell that shouldn't be possible. This has not always been a problem..., Excel 2010 opens this just fine. (It just displays like Calc - showing a split screen.) However at least Excel 2019 complains about a corrupt view. It then "deletes" the "corrupt" view and so the user loses the freeze line(s). Probably generated by multiuser online, this can also occur during a file-open of an already "corrupted" document. Steps to reproduce 1.) open custom frozen spreadsheet.xlsx in LO. (Excel already complains it is corrupted.) 2.) save and reload in Excel. LO has not "fixed" the document, but still round-trips it corrupted, showing that is it possible to potentially create a corrupt xlsx file in certain circumstances. [When opening the document, notice that the bottom right pane is showing cell A1 again. That shouldn't be possible for a frozen sheet. The freeze is still in place, and will "activate" once you move right/down enough.]
Justin Luth committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/commit/5ef44a0b2ad238fbd13196e2f602de71f42a34d1 tdf#165130 sc: prevent pane's topLeftCell from being in frozen zone It will be available in 25.8.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.