The company I worked for for 40 years had several 5 axis milling machines they used to machine the twisting blades on the centrifugal titanium compressor wheels for the gas turbine engines they produced. (The 5 axis were X, Y, Z, tilt, rotation.)
A safety engineer reviewed these machines and decided they needed to have multiple safety switches installed to protect the operators and the machines from harm. On his advice, this was done.
Because there were so many different switches that could shut the machine off for any number of reasons, one switch or another was always shutting the machine down. When one of these machines shuts off in the middle of a cut, it ruins the parts being machined.
The titanium forgings cost over $1000 each and four parts were being machined at a time so every time this happened it cost $4000 plus the maintenance man's time to figure out which switch was causing the problem and repair or replace the switch.
We ended up removing most of the switches, keeping only the ones that kept the operator safe.
Lesson learned? There can be too much of a good thing.