dweb check if you run out of ram, if you do is a tricky situation, either set it to restart always or add swap or reduce the oom to -1000
All solutions have their risks, I did reduced the priority but also increaed the ram of the server to 128gb on my setup .
Now if you add swap is not the best yet because website containers will swap like crazy and then you have w/a.
My suggestion, setup monit I have posted some examples here , get notified when and why it fails and it will also restart it, once you figure it out apply the best fix you think.
If you run 10 websites with 512 mb ram on a 4 GB server you probably have oom issues, I am not sure if OOM is good or a bad thing but I like it when it kills lsphp specially during floods or other issues .
With monit you can also set rules to gracefully restart it before oom, or restart another service that consumes ram .
