ZxMobile wrongly reports Mobile Device Managegement feature is disabled

We have a multi-server installation running CentOS 6 x86_64 on 17 Zimbra servers of which 9 are mailbox servers (2 mailboxd are deliberately stopped).
We run Zimbra 8.0.4 OSE and ZeXtras 1.8.17.

A month ago, when we run ZeXtras 1.8.15, we had a few users with EAS 14 beta turned on.
After upgrade to ZeXtras 1.8.17 the MDM feature was disabled by default, and the web interface correctly displayed a warning.

So we went to this backend, and checked the box to enable it..
A warning came up, pressed ok, and then saved the new setting.

But even so, when I find a user and change e.g. default mail retention, it still reports that MDM is disabled on the backend.