Hi,
Troubleshooting network problems : you shouldn't be using them to get needed info. Which means you have to use most important interface : the console access. That one will stay functional when an interface goes down. You'll be able to check the logs and other system specs - the place where all the answers are. You'll see that the system isn't down at all, most probably only the NIC (driver).
Also : is your WAN not a Realteck ? Then swap WAN and LAN interfaces. Realteck NIC's are strange animals. I'm using several of them right now. Other, probably most, came in from Amazon, lasted a day, and are piling up in some box somewhere, being completely useless. You shouldn't doing complicated things with them like "heavy load" and VLAN's at the same time ... that's asking way to much.
Btw : have a look in this forum. There are post that mention an alternative Realteck driver with rather good results, better as the build in stock driver.