Ref.: #34193
Background/Details:
On the router with RTC (Real-Time Clock) battery running out or malfunction, could possibly cause an unexpected DHCP lease time, that is not follow the DHCP server settings in the router.
The user might observe the DHCP client in the router’s Client List showing lease times of several thousand days (picture below).

We have developed a special firmware, 8.5.2s038, to mitigate the issue. The fix has been added to the 8.5.3 GA firmware release.
Affected firmware version:
8.5.2 GA
Affected models:
Models with RTC
Fixed in firmware version:
8.5.2s038