Office 2021 - Specifically word and excel very slow to open files on shared Synology DS218+ NAS

Beaglebud 1 Reputation point

As background. I am running a Dell XPS 8940 desktop with Windows 11 Pro OS version 22h2 Build 22621.819 (updated one week ago). Computer has 32 GB RAM and 2 TB main disk plus two external USB disks and an Synology DS218+ NAS with 4TB disk space only 1/2 full. I have Office 2021 installed with the most recent update.


For sometime, word and excel have been extremely slow accessing files on my Shared NAS via a mapped drive. It will take anywhere from 20 sec to 1 minute to open a file whether I open directly through Windows file explorer or via the Word/Excel file command. Once the file is open, I can open other files normally within a second or two, but if I close the program(s) down and reopen, the first time I attempt to access a file on my NAS through a Mapped Drive, it once again is extremely slow. I totally uninstalled Office 2021 and did a clean install and have the same problem. When I open either Word or Excel in Safe Mode, the problem persists, however, I disabled all add-ins just in case and no relief.

I have spent considerable time researching and have applied all the registry fixes, office fixes, Windows fixes and procedures suggested to solve the problem, but nothing seems to help. Oddly enough, I have Office 2010 with windows 10 on a second desktop and it runs like the wind and opens files through mapped drives normally.

At first, I thought it was a Synology NAS problem and worked with Synology Techs both through chat and providing them access to computer remotely. They found no problems with the NAS configuration. I am fairly confident the NAS is NOT at fault as every other non-office program such as Adobe programs and other stand alone programs have any issues opening files on my NAS. Additionally, I mapped a drive to a folder on my local hard drive and the same problem exists-files opened with Word and/or Excel are very, very slow to open the first time. It is as if the office programs have to go through some kind of "connection routine" to connect to mapped drives.

Another reason I am fairly positive it is not the NAS is that I also notice through my research and in this forum, this issue has been going on for several Office versions, different computer configurations, and different mapped shares. Additionally, what seems to work for one doesnt work for others.

I would think that the very talented Microsoft software engineers could solve this issue since apparently Adobe and other vendors have. I am at my wits end and I need help - not condolences. Standing by for solution(s).


Microsoft Office Online Server
Microsoft Office Online Server
Microsoft on-premises server product that runs Office Online. Previously known as Office Web Apps Server.
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  1. Ceasar Chen_MSFT 4,391 Reputation points

    Hi, @Beaglebud-0871
    Possible methods:

    1. In Excel - Advanced - check this dialog box
    2. Check the printer, update the printer driver
    3. Try to use Process Monitor or packet capture tool to grab the log, this method recommends you contact Microsoft phone support:

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