Flex 100 Gradually Gets Slower Until Reboot

Hi,

We have a Zyxel Flex 100 that seems to have an issue in that it gradually slows down web/vpn/voip calls etc over the space of around 10 days.

After 10 days we then have to reboot the device by pulling the plug as the web gui does not respond nor does ssh.

Once rebooted everything goes back to normal speed and voip calls are great but gradually the performance drops over the 10 or so days until we have to reboot again.

Is there a way to look at what is causing the Flex to perform like this and to find just what he culprit is ?

PS it is on the latest firmware and has around 10 internal users and 4 vpn remote users

Many thanks for advice.

Andrew