A mod would be a more likely explanation than whatever other 'sinister' explanation you're envisioning.
Do the following:
Delete your ModuleManager.ConfigCache file and then run the game. (this is necessary to force Module Manager to reapply all patches which it will then log to your log file)
Check your log file and search for Squad/Parts/Resources/FuelCell/FuelCellArray. You want the lines that end with something like '(applying some patch name) to Squad/Parts/Resources/FuelCell/FuelCellArray'
Those are the patches that are modifying that part.
Example:
In the example above, IoncrossCrewSupport mod has applied a patch to the FuelCellArray PART node. (among other parts)
Ok guys, re: stock radiators. They aren't going to protect an ablative heat shield from heating up to its ablation point because they don't even kick in for that part until it meets or exceeds a threshold based on its max temperature. Its ablation point is considerably lower than that. The entire craft will heat up past the shield's ablation point before the radiators kick in no matter which kind of radiator you use.
Starwaster's post in The fuel cell Anomaly! was marked as the answer