[BUG]Set-PnPWebTheme results in Unknown Error

[pmolstad]

Notice

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1. Are you using Invoke-PnPSiteTemplate or Get-PnPSiteTemplate? The issue is most likely related to the Provisioning Engine. The Provisioning engine is not located in the PowerShell repo. Please report the issue here: https://github.com/pnp/pnpframework/issues.
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Reporting an Issue or Missing Feature

Please confirm what it is that your reporting
Just recently, we started having issues running Set-PnPWebTheme cmdlet after successfully running Invoke-PnPSiteTemplate. There have been no changes to our script which has successfully run in PowerShell 5 and 7 for over a year. The script now fails only on the Set-PnPWebTheme cmdlet which is reproducible outside of the script. We have an existing custom theme that is applied to all of our Communication sites at the time the site is created via an XML provisioning template. Only recently, do we now have to apply the existing theme manually via 'Change the look' since the cmdlet is no longer executing successfully. We have found that the cmdlet successfully applies out of the box themes like 'Teal' but fails to apply our existing custom theme as it has done successfully in the past.

Expected behavior

Please describe what output you expect to see from the PnP PowerShell Cmdlets
As in the past, the expectation is no error message with the existing theme applied to the newly created site.

Actual behavior

Please describe what you see instead. Please provide samples of output or screenshots.
The script fails displaying the following message and the existing theme is not applied.

Set-PnPWebTheme : Unknown Error
At line:3 char:1

• Set-PnPWebTheme -Theme $theme -WebUrl $site

•   + CategoryInfo          : InvalidOperation: (:) [Set-PnPWebTheme], PSInvalidOperationException
    + FullyQualifiedErrorId : InvalidOperation,PnP.PowerShell.Commands.Branding.SetWebTheme
  
  

Steps to reproduce behavior

Please include complete script or code samples in-line or linked from gists
https://gist.github.com/pmolstad/cb6999dde1a87fc59b12c2a738eb877a#file-applyexistingcustomtheme-ps1

What is the version of the Cmdlet module you are running?

(you can retrieve this by executing Get-Module -Name "PnP.PowerShell" -ListAvailable)
PowerShell 5 - version 1.12.0 (Core,Desk)
PowerShell 7 - version 2.12.0 (Core) / version 2.4.0 (Desk)

Which operating system/environment are you running PnP PowerShell on?

• Windows
• Linux
• MacOS
• Azure Cloud Shell
• Azure Functions
• Other : please specify