Why are Excel files opening slowly over the network?

Question

Microsoft Office

Good afternoon,
There was a problem in the network - Excel files (.xls) located on a network share (Windows Server 2012R2) take an extremely long time to open if they are already open by someone else. If the file is not open anywhere else, it opens immediately. The file size is very small - less than 1 MB. Clients - Windows 7 Ent x32, Office 2010 SP3, Office 2013.
There are no errors in the log. Where should you look?

Answer 1

What we currently have.
The file opens normally after resaving. The format of the book has not changed, the file is still the same .xls. Just saved it to a new file and deleted the old one.