One of my ESXi hosts went down last night, and where offline all night.
The crash happened because of a transfer of VMs that was too large (2,5 TB).
The issue have been resolved.
There was also some issues with NGINX on the web server after the reboot. The issue was caused by a website that was removed. NGINX was expecting the website, and did not want to start without it. After removing it from the NGINX config, it started up just fine.
The issue was not found until after a complete reboot of the ESXi host because NGINX was running when the site was removed, and did not detect the change until the web server VM was rebooted.