Columns hiding automatically

Hello,

I have a huge complex spreadsheet shared with multiple users via Sharepoint.  I have columns and rows protected.  I have a few columns that are hiding themselves on their own.  I am able to unhide them again by unlocking the sheet, but they randomly hide again (sometimes not the same columns).  Some adjacent columns do contain formulas and there are some hidden columns nearby.  Has anyone else had a similar issue?

Thanks,

Andrew