Rows of data moving

Greetings to all,

At my work we have recently started using Smartsheet.  We use it on a simple level, i.e. two or three users can update the same spreadsheet at the same time.  We're a transportation company and we use the spreadsheet to schedule our runs and and update current runs after completion.  What we have noticed, and it continues, is that blocks of data, i.e. several consecutive rows,  appear to move to a different location (usually lower) in the same sheet.  The data doesn't corrupt it simply 'moves.'  Has anyone seen similar occurrences of this nature?  I can't help thinking that it's a user error that we can't resolve.