Ah, good point. So @nschiett that’s referring to this line of your Stan code, which is treating 10 and -5 as integers:
real k = 8.62 * 10^-5; // Boltzmann constant (eV / K)
So you can just do real k = 8.62e-5; (I think the CRAN people made a typo and put 8.65 instead of 8.62 in their comment)