Resetting SNAP analog modules can cause unexpected behaviors on some Ethernet brain features. Analog modules can reset if there is low voltage, or if the module is unplugged from the rack. They display an "invalid float value" such as ‑1.#QNAN, ‑1.#QNAN0, or ‑nan.
As a result, if one of these invalid float values is used as the input to a PID loop, the output option for when the input is out of range may not be applied since the PID loop does not recognize the invalid float value as an out-of-range value.
Prevent modules from going going off-line by making sure racks have the correct voltage supplied to them. Be sure to measure the voltage on the rack while all modules are installed.
Also, verify all configured modules are installed.
Opto 22 has resolved this issue for SNAP PAC and Ultimate I/O brains.