Salesforce 'Insufficient Privileges' Error Creating or Updating a Record After Partial Sandbox Copy Refresh

This error happens when the associated record that is usually populated via an automated process is not copied during the Sandbox copy process.

For example, we have an Apex Trigger that is populating a Contact Lookup with a static value, ex: 003X00000XxXXXX. When the affected user attempts to create a new record via the UI, they see an exception (Insufficient Privileges) on Save.

How do I confirm for sure whether I'm affected by this issue?

Option 1

The System Administrator or a User with API access can attempt to create a record via the API. This will give you the offending record that is causing the exception.

Example:
1.Login to Workbench
2. Click on Data | Insert | Single Record
3. Populate Required Fields.
4. Save.
5. You will see an error similar to the following:

If you navigate to the contact record via the UI, you will see the following error:

Data Not Available
The data you were trying to access could not be found. It may be due to another user deleting the data or a system error. If you know the data is not deleted but cannot access it, please look at our support page. 

This confirms that a static value is indeed being populated via an automated process on record creation/update.

Option 2

Disable the Apex Triggers associated to the object one by one until you no longer get the error. You can also enable Debug Logs for the affected user. This will narrow the cause of the issue to the Apex Trigger, which you can then address by modifying OR disabling.

Resolution:

1. Isolate and disable the automated process populating a static value on the record during Create/Update.
2. Isolate and modify the code.

Is this Working As Designed?

Yes. Please refer to the following article: Records copied when you refresh Partial Data sandbox