Very nieche but blows up nginx: I've had it happen a few times last months, and a friend of mine tuesday as well, but there are some instances that, when installing a new cert for an unrelated subdomain (I believe in my instances it were always subdomains), the SSL certificate files of a totally unrelated domain disappears while the config include is still there, (resulting in EMERG -> webserver down). Sometimes it will work again by just reinstalling a new cert but there were also some instances I had to manually get rid of the include.

Really vague, sorry, but I can provide you with the domain names it happened on Tuesday if thats of any help. Always happens on the moments you don't expect it and has quite an impact when it brings nginx down.