Dynamic routes from OSPF disappear

Hi. We have two routers and 7 machines with bird installed (7 machines <-> router <- Internet -> router <-> 8th machine) that work without problems. When I've added 8th machine with Ubuntu 14.04 and bird 1.4.3, everything was working for about one hour after all routes announced over OSPF disappeared, also own routes were not announced. By enabling debugging (debug ospf1 all in birdc) there are no messages that would indicate an error (just normal hello exchange and OSPF LSA announcements). By restarting the ospf1 protocol, the OSPF routes are exchanged and it works for another hour or so. Anybody experienced the same behavior? Best regards, Gregor Kališnik