N300A IP reboots

[#1]

I have a Cudy WR3000s running OpenWrt. When I look at the System log I see that every night between about 00:00 and 04:00 lan1 link goes down then up again over a period of about 18 or 20 seconds. The only thing connected to lan1 is my N300A IP VOIP base station. If I manually reboot the N300, the system log shows the same sequence of messages in about the same time, so it looks as though the N300 is doing a reboot every night. Looking at the N300 interface there don’t seem to be any settings that may control this.

Whilst losing my telephone connection for about 20 seconds every night when I’m asleep is not a great concern, I’m interested to know whether anybody else has noticed similar behaviour. Is this normal for the N300A IP or do I have a problem?

[#2]

I have a WR3000H.  running Openwrt as a bridged AP. with an N300 connected to lan2. Not noticed it before but just checked the log and mine does the same. 

[#3]

I used to have N300 but now have N510ipPRO which is actually very similar.

That seems to do a time sync every night shortly after midnight, maybe the N300 is doing something similar and that creates the symptoms you see?