My vault died overnight.
My ssh showed "Killed" on the last line
I went back through my VM metrics that aws provide and found that I had exceeded my CPU credit balance due to high CPU usage. Guess there must be some conditions in the vault that cause high CPU usage. I suspect @Southside, this would be what your problem was too.
Maybe due to excessive churn or similar. So the free tier may only be useful when the network is large enough to not have excessive amounts of churn. OR there is a bug
I've restarted my node, my CPU credits have risen since the vault automatically being killed CPU usage monitor. Hopefully this doesn't happen often. It was the 1st time in over 3 days.