OS Server and excel 2011 issues saving over network

This seems relevant to issues we're having with saving excel (2011) files from various client's (all Yosemite) on our server running Yosemite with OS server app. All apps and OS up-to-date on both client (OS 10.10.3) and server (4.1). This was working fine in OS 10.6.8 running os server.

Have found reports of people having fixed issues by updating both OS and server app (http://answers.microsoft.com/en-us/mac/forum/macoffice2011-macexcel/issue-when-s aving-excel-files-from-mac-os-x-server/e…)

Haven't found a working solution for related error massages from excel on our client(s) (e.g. Warning: Can save, but not re-open file; please close file and open) so far. Have tried corrected user ownership and privileges in server app -to no avail-. Running everything over afp not over SMB is of for all shared folders.

Only weird thing is that App Store (on the server) suggest to update to server 2.3, clearly an old version of the server app.

Anyone having found a solution or having the same problem? and able or willing to help resolve this issue?