L2TP/IPsec VPN server issues

Hello, community. I hope you can help me with this issue.
My company has approximately 30 Peplink Balance 20 deployed on our customer’s premises and they are working as expected. The issue is that from time to time the VPN server on a random Peplink doesn’t respond to connections request. For example, I can connect right now to most of them via VPN on my work computer but one of those doesn’t allow me. It says the LT2P server did not respond, but sometimes it lets me connect successfully but extremely slow. Why does this happen? Do Peplink routers need to be rebooted from time to time to refresh the services or something?
This is not the first time this happens to me and it gets fixed with a reboot. Also when the internet goes down on a customer the router loses the quality of voice in our phones. It doesn’t always happen but it happens.

Check the DHCP range to make sure it is large enough to provide a new IP address each time a remote user logs in. Also be sure you are up to date on firmware, prioritize VoIP with a QOS application rule, and follow these recommendations here for sizing deployments.

If the problem re-occurs, please obtain a diagnostic report before rebooting under: Status> Device and open a support ticket with us here so we can investigate the issue.