They do seem to be good supplies, but they are not infallible. I’ve had two Opto 5VDC supplies die on me - one just stopped supplying power - fuse was good, the other lost voltage regulation and would cause some of the modules to read wonky. This is nothing compared to the failures from old 25 year old non-Opto open frame supplies (±15/5VDC) that are powering some old stalwart B2 controllers that we still service - we’ve been changing these out for some by Sola.
For my original request, we changed the design to not require an active standby power supply. This is for a CHW pumping application for a data center. We added a mechanical relay that will activate a fixed speed input on a couple of the drives if the relay drops out. This will give them some flow while a tech changes out the power supply, if it is ever needed.