Post-Sync scripts stopped working after upgrading to Horizon 7.12

After upgrading to Horizon 7.12, our Post-synchronization scripts stopped working, and pools would ERROR out when provisioning instant clones.

Turns out, its a bug in Horizon 7.12.  I saw a few of you with the same issue in the following thread, but I'm starting a new post for better visibility since it was off-topic.

   Ref: C:\Windows\Temp\vmware-viewcomposer-ga-new.log ... |VMware Communities

The bug is that the Horizon agent copies the script to c:\windows\temp\vmware\ folder...but fails to copy it successfully.

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The DEBUG log shows the FAILED Creating Post-Customization, Hash File: 0x80070003  error.

If you manually pre-copy the actual script file into the c:\windows\temp\vmware\ folder before creating your snapshot, it will work as intended.

I've opened a Support Case with VMware and will post the solution once I get it.