I faced almost same problem & problem resolved after fresh installation of Openhab 2.
I am not sure about why this problem arises in my previous setup, but it was started after enabling WIFI connection. So during fresh openhab setup I first applied statistic ip in dhcpd.conf file before doing anything else. & It works.
https://community.openhab.org/t/solved-how-to-set-static-ip-of-eth0-port/62974/2