This is weird.
Firmware version is too old, so it is advised to upgrade it to recommended version. Confirm the AP models connected to your ZD and I will provide you recommended version.
Please note, it may or may not fix your issue because we don't know the root cause of this problem. It would be best if you could open a support case and let support check the issue.
Syamantak Omer | Community moderator | Sr.Staff TSE | CWNA | CCNA | RASZA | RICXI