I came across an issue with the Excel version of Office 365 ProPlus, as below described.
A.xls(x) contains formula that links to B.xls Sheet1. When working on A.xls. I decide to navigate through windows explorer and open B.xls(x). Once I do all references to Sheet1 turns into #REF of A.xls(x). And naturally all values that were previously correct now returns #REF. Even without making any changes to B.xls(x), just opening the file cause this problem. Both these files are on the mapped network location within the same LAN. User is on Win7 & Office 365 ProPlus. The server is running on Windows 2008 R2 with no office installed. This occurred to users who are member of the AD and in Workgroup. We have tried re-installing, repairing, etc. but the problem remains the same. But if the files were on the local HDD, we didn't face the same issue.