Thank you @mirzak and @tranchitella. You are right this is not the answer we were looking for but we understand and agree we need to get the environment upgraded.
When I look at the upgrading instructions for 1.6 one of the first steps is cleaning up the devauth database, however the link to the corresponding mender server troubleshooting page is broken. I fear upgrading from a version this old is likely to also have issues and would appreciate any suggestions about how to approach this.
We are inheriting this setup and would like to move to hosted mender instead to avoid problems like this going forward. I see a recent thread here discussing the multi step update required for devices. If I understand correctly, the idea is to re-authorize (or pre-authorize) devices on the hosted server as opposed to any kind of database migration. Is that correct?