They should all fail in the same way. Rely on them. An object or bit of information most needed will be least available. Any device requiring service or adjustment will be least accessible. In any human endeavor, once you have exhausted all possibilities and fail, there will be one solution, simple and obvious, highly visible to everyone else.
Badness comes in waves.
At the source of every error which is blamed on the computer you will find at least two human errors, including the error of blaming it on the computer. Any system shich depends on human reliability is unreliable. After months of training and you finally understand all of a program's commands, a revised version of the program arrives with an all-new command structure. The first myth of management is that it exists. It works better if you plug it in.