Worse than that, the server can change it's response based on user agent so you need to curl it to a file first, a browser could be served a completely different response.
"Sorry to the inhabitants of the proposed Stevenson Avenue, your road has been cancelled due to leaves on the plot, a member of staff will guide you to our tent replacement service."
So next I'd be checking logs for sata errors, pcie errors and zfs kernel module errors. Anything that could shed light on what's happening. If the system is locking up could it be some other part of the server with a hardware error, bad ram, out of memory, bad or full boot disk, etc.
Worse than that, the server can change it's response based on user agent so you need to curl it to a file first, a browser could be served a completely different response.