Draytek 2766 and SiP trunks

Hi I have a Draytek 2766 connected to a Gamma Sogea DSL line for SiP trunks. It has been configured and works well. However on two occasions the Lan 1 config has changed back to the default 192.168.1.1 and DCHP enabled.<br/>
The Wan settings, username and password, firewall,NAT settings are not affected? If I remote in and change Lan 1 to the correct ip address it then works OK again.<br/>
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Obviously when the Lan changes the PBX loses the SiP trunk as its not on the same Lan as the PBX.<br/>
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It seems to last about a week before it resets, I have checked the settings but can't find anything wrong....is there a timer or something?<br/>
Firmware is 4.4.3_BT.<br/>
Any help welcomed<br/>
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25.01.24 I have now defaulted router and reloaded Firmware 4.4.3_BT just in case there is any corruption in the build......see what happens