Doesn’t look like a problem with config. Looks very much as if your PC is being configured automatically once you boot the Duo board up, and after a while something resets the address.
This can happen in several cases.
For instance, if your computer wants to renew/rebind/confirm the address (it happens at least once at half the lease period) while the DHCP server isn’t responding already.
Requires further investigation.
Anyway, you can inspect what’s happening at that moment if you hook a USB-to-TTL converter up to the UART line of the board, this may help.