The Cam lose the Gateway IPv4 configuration...!!!

Good Morning,

I have several DS-2CD2142FWD-I cam installed on my network but sometime, without reason the cam lose the Gateway IPv4 address configuration. Field Blank!! The DHCP is enable.
I must reboot him, and the cam find again the gateway address. This situation is random and occur for all the cam.

Any suggestion to fix the problem?

Thanks in advance
regards
Gianluca