Errors when sharing Workbook

[Lambs]

Hi,

Overthe last few days, a shared workbook which we have been using happily
for several years, over several versions of Excel, has suddenly started
throwing up erroneous information. We cannot yet be sure if information is
being duplicated or misplaced, because of the size of the table and volumes
iinvolved. Filters are on, panes are frozen. It's primarily date information.
We think it's just ending up on the wrong rows.

Also, recently-saved information is not appearing on other peoples' versions
when they save.

I'd be grateful for any advice people may have.