Slow loading/browsing of network files in File Explorer

Any details, did it work fine before, over network, over wan?  How many files in the folder?

How does something small \\server\c$ work

Is it an older server running older versions of SMB?

It is only a 2 week old machine and the user doesn't recall when it started or if it has always been sluggish.  It does appear to only be when there are 30ish or more files and sub-folders.  I might add it is slow on any mapping, regardless of which resource/server.  Browsing a local drive is lightning fast.  I updated the NIC and that didn't change anything.

what version of server is it connecting too?

Go to Settings -> Network and Internet -> Status -> Network reset -> confirm
Open IE properties -> reset IE

Ping to server where folders are located. What are the values of ping?

There are 2 separate resources and they are both Synology NAS devices that the client is mapped too.  All other clients can access the NAS's just fine though.  Network and IE reset did not work.

Ping to server where folders are located from affected machines. What are the values of ping?
Try to remap both network sources.
Is that device connected via WiFi or LAN?

Sometimes Anti Virus installations can become buggy and since they usually scan just about everything you open, you could experience high degree of latency especially traversing folders. Uninstall the AV from one client and see if that helps.

Suggestions from another discussion:

I would start by comparing the two user accounts in Active Directory:

Do user A and B have the same logon scripts? If not, compare the two logon scripts to see what's different.

Do user A and B have the same "Member of" membership to security groups? If not, find another person who does, and see if this problem exists for that user as well.

Do user A and B get the same Group Policy Objects applied at logon? To check this you can use Group Policy Modeling Wizard to see which GPOs apply to each person.

If user A and B have the same permissions, group membership, group policy objects applied, then let's look at the roaming profiles. You might even first test this by renaming the C:\User\UserA\ directory on a local system just so Windows logs them on with a temporary profile. THe benefit to this would be that if their network shares are NOT slow when using a temporary local profile, then the issue is definitely within the roaming profile folder or preferences itself.

If the problem does persist even with a temporary logon profile, then it's still having to do with permissions in some way.

If you cannot find any difference in setup, permissions, or group membership, then I suggest removing/renaming and re-creating a new user profile and roaming directories for the affected user.

A few people were also helped by disabling SMB signing.

Have you checked DNS? Make sure that it's trying to do IPv4 before IPv6?

No other suggestions worked.