dyndns on webserver causes router to disconnect

I have a small webserver configured on my Raspberry Pi (Debian, Jessie). Alongside the services Apache, MySQL, PHP etc. there is a Dynamic DNS client 'ddclient' running as daemon to check the public ip to my domain every 5 minutes. The service works fine but has the nasty side effect to cause my router (FritzBox Fon WLAN 7360) to disconnect from the internet every few minutes. I'm pretty sure that ddclient is the reason for the interruptions because this problem came up since the service is running. What can I do to solve this? Is it technically possible for ddclient to be the guilty one? Does ddclient have a wrong configuration? Is my router broken? What if I set the ddclient service as run_ipup="true"? Will my raspberry automatically update the IP-address as soon as it changes? Here is an excerpt from my router log. 31.03.17 11:45:38 Internet connection was successfully established. IP-Address: xx.xx.xxx.xxx, DNS-server: xxx.x.xxx.xxx and xxx.x.xx.xx, Gateway xx.xxx.xx.xxx, Broadband-PoP: ewetel.dsl-e320-02-Bremen 31.03.17 11:45:34 DSL is available (DSL-synchronization exists with 11102/1040 kbit/s). 31.03.17 11:44:50 Timeout with PPP-negotiation 31.03.17 11:44:49 Internet connection was disconnected 31.03.17 11:44:45 DSL does not respond (no DNS-synchronization) This is only an excerpt of dozens of those messages. Note that every time the router reconnects to the internet the IP-address changes. Please help. Thanks!! **EDIT**: Regarding to Eamonns answer I have set up my a dynamic dns service using curl and crond. Thanks Eamonns, you've helped me alot!