A few months ago, we reported on an issue with Microsoft OneDrive for Business where it modifies certain file types as it syncs them between PCs, by adding meta information to each file. So far, this issue has not occurred on the consumer version of OneDrive, at least not when syncing files between PCs and laptops.
A new user Tony joined our forum to tell us that the Microsoft community forum is flooded with issues about the consumer version of OneDrive corrupting files. So we repeated our test by syncing over 10 different types of files between Windows 7 and 8.1 PCs and running MD5 checks, but everything seemed to sync just fine with no MD5 discrepancy.
When I checked what was going on in the Microsoft Community forums, it turned out that the problem seems to be specific to editing Excel files through the browser using the web based version of Excel. Once any Excel file is edited through Excel online, the resulting file OneDrive synced to the PC would become corrupt, at least with OneDrive for Windows 8.1.
To try to replicate this issue, I created an Excel file in my personal OneDrive folder, added digits to a few cells and then edited that file in Excel online by adding digits to a few more cells. Once that online edited version synced back to my laptop, the resulting file gave the following error:
The following uncut video demonstrates this bug:
For this demo, I used a laptop running Windows 8.1, Excel 2013 and my personal OneDrive synced folder. This bug also seems to vary intermittently from computer to computer. For example, when I booted my desktop PC into Windows 8.1 and repeated this test in Excel 2013, the bug did not occur no matter how many changes I made to the Excel file online. On my laptop, every single Excel file I edited online resulted in the offline synced file getting corrupt.
According to the most of the feedback reported on the Microsoft community forums, this bug seems to be specific to OneDrive for Windows 8.1 and does not occur in Excel files synced with OneDrive on Windows 7. Word files edited online do not appear to be affected from my testing, but there are a few reports of various Microsoft Office file types including Word becoming corrupt once synced back to the PC.
For those affected, one workaround is to open the file online and save it to the PC. For those with a large number of files on OneDrive, another option is to sync OneDrive to a Windows 7 based computer.
Update 2nd Sept '14: According to Arcadiy K from Microsoft, this issue has now been fixed such that files edited online will no longer result in the synced offline files becoming corrupt. This fix does not currently repair existing corrupt offline files, so they will need to be manually downloaded from OneDrive online.
