ZKTeco K40 attendance device timeout

[KristianLGeorgiev]

The problem

For sime time now we have been working with the ZKTeco K40 attendance device and we have discovered a glaring issue. In the Settings -> Ethernet menu we have turned DHCP on, we have set our IP address, DNS, everything is configured correctly.
When we try to ping them we see a response.
But after some time (a couple of hours or sometimes even minutes) when we try to ping them again we see that they are unreachable. We go to the device itself, in the Ethernet settings, and we see that everything is how we configured it to be, but the IP address and Subnet mask are 0.0.0.0.
We have another device, but on that one we turned DHCP off and configured everything. This time though, the IP does not reset to 0.0.0.0, but we still cant reach the device..
Any advice on this matter will be appreciated.