ABM/ASM Release OR Un-assign Prior Repairs?

[bootrec]

We have just over 1,000 iPhones in Jamf for our staff. Our staff are responsible for repairs themselves by contacting Apple directly. We have experienced some very confusing and convoluted issues with Apple in this regard, and I'm still unclear how to avoid future issues.

I myself have sent a few iPhones for repairs over the past 2 years. The only information Apple provides is to "Remove your iPhone from your Apple ID". Well, I can't do that if the iPhone was set up by another employee, and we have our PreStage Enrollment profile configured with "Prevent user from enabling Activation Lock" set to enabled, and "Enable Activation Lock on the device (ASM/ABM)" set to disabled. 

Yet, inevitably, after we send the iPhone in for repair, we get the iPhone returned to us with a note that they couldn't do the repair or replace the device because either the iPhone has remote management, or it's assigned to ABM/ASM. 

My question is, how do I know which of these actions I need to do prior to sending an iPhone in for repair? Do I un-assign MDM from ABM/ASM, or do I release it? If I release it, it's permanent, I can't re-add without Apple Configurator, which is a big issue for staff taking care of their own repairs, in our remote work environment. If Apple replaces the iPhone, they normally assign the replacement serial number to our ABM/ASM, but the last one a staff sent for repairs, Apple did not (because they returned the iPhone twice and I was explained by Apple that multiple back and forth screws up their process).

Any inputs from folks who have experienced this would be appreciated, thanks.

[Bol]

I’m guessing the only option would be the user to remove the device in their iCloud account

OR

I haven’t test these options in a while but could this have the desired effect if applied?

[PaulHazelden]

In the past when we have had stuff go back to Apple for repair, we have un-assigned the device. Then when it is back you can simply re-assign it. If your end user is going to reset up the device once it is back, you will need to re-assign before they do this.
There should be no need to release the device, unless you are told to do so by Apple. I would only expect to see this if they are sending you a new device, and they are keeping the old one.