I've had two different SLCs with RTD modules fault for no obvious reason. One occurrence I got the opportunity to examine logic/rtfm and I believe I found some weaknesses in the code that could allow the module to generate a major fault, but I don't recall it being the code you described. It was leased equipment so I didn't change any logic...it happened occasionally (every few hours) for a few days until we found one bad RTD cable and then never returned. I think the bad RTD was freaking out the card and the error was along the lines of 'card failed to respond to a command' or something like that.
In the other case, it was brushed off as a fluke and the tech had already cycled to key switch so I never investigated...
I would weigh the cost of a 2nd occurrence (downtime/waste) against the cost of a new card before throwing parts at it.
