Dell EMC Unity: Users cannot access CIFS or SMB share on NAS Server (Dell Correctable)

After upgrading to Unity OE 5.2.0.0.5.173 users with a Kerberos token greater than 16 K cannot access CIFS/SMB share on Unity NAS Server.

Error message the user might get is following:

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Windows cannot access \\nasservername\share

Check the spelling of the name. Otherwise, there might be a problem with your network. To try to identify and resolve network problems, click Diagnose.
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For a customer to, encounter this issue, three conditions must be met:

• Array is on Unity OE 5.2.0.0.5.173
• Customer is using SMB file sharing over Kerberos Authentication.
• SMB users with Kerberos token size over 16k

Issue is caused by a new function that was added in 5.2.0.0.5.173 code that occurs during sessionSetup.

When a Kerberos token exceeds 16 K the Unity responds with STATUS_INVALID_PARAMETER during sessionSetup.

An additional check was added in 5.2.0.0.5.173 that results in the STATUS_INVALID_PARAMETER error prior to checking if the request would need to be handled over multiple sessionSetup calls.

Fix:
The fix is available in OS 5.2.1.0.5.013 (5.2 SP1).

Workaround:
1. Reduce user's Kerberos token size by reducing number of groups (unused groups, and so on) or by removing unnecessary SIDHistory attribute. 
2. Access SMB server over NTLM (that is over IP).
3. Fail over to DR array running 5.1.x code, if available.