Summary of the problem and what "fixes" it:
At seemingly random intervals, all interfaces report high latency and/or packet-loss. I can temporarily resolve this by restarting all my OpenVPN sessions. This temporary fix may last hours or sometimes days before it becomes an issue again. A system reboot will usually prevent any issues for around 4-6 days.
Current version is 2.7.0 CE, but this issue has persisted from around the later v2.5.x releases, maybe before - not clear as I had ISP issues on top at that time (now 100% resolved). The current install is a fresh install because the upgrade from 2.6.0 did not work... so the config is a backup from the old install before wiping it.
System spec: Intel i5-4430 CPU, 8GB RAM, 120GB SSD, 6x Intel 82583V NICs (4 in use).
This is a dual WAN setup, with failover to LTE WAN. I have five OpenVPN...