port forwarding meshed up

recently changed hikvision ip cube camera'S (DS-2CD2412F) port and then after it does not work. i also changed PF in router. it works only for 1 to 2 hrs. then it caot be access from LAN or WAN. same problem with default port 80 now. ports are 80, 554, 8000. all other PF for other device in router works good. i tried too many ports. also changed and tried firmware 5.1, 5.2 5.3 of ip camera. but no luck. it works only ( with any http port) for 1 to 2 hrs after resetting camera to factory settings. after resetting port shows open status but after 1 hr. something its closed. if i use same port with my other device it works fine.

pl. asap