Update Mobile Static Group says Failed but was successful.

[TexasITAdmin]

Using a CSV of mobile device serial numbers.
Adding to an existing mobile device group.
Message in the MUT says "Update run failed. Check the MUT.log for details"
MUT.log says:
2020-02-05 03:31:00 [INFO ]: <mobile_device_group>44</mobile_device_group>
2020-02-05 03:31:24 [INFO ]: Token has 1542 seconds left to live. Proceeding with current token.
2020-02-05 03:31:24 [INFO ]: Beginning CSV Parse - Scope update.
2020-02-05 03:31:24 [INFO ]: Submitting a PUT to https://xxxxxxx.jamfcloud.com/JSSResource/mobiledevicegroups/id/44
2020-02-05 03:31:52 [INFO ]: Successful PUT completed. 201.
2020-02-05 03:31:52 [INFO ]: <mobile_device_group>44</mobile_device_group>

Doing the reverse (remove from group) gives the same result.

[TexasITAdmin]

I missed the one that already existed somehow.