When the argument for sinh is so large that it would overflow an ordinary float, it causes a Lisp error instead of overflowing to a bigfloat.
sinh (1e3); => CDR: 1000.0 is not a list
Backtrace shows that's in the bigfloat sinh function FPSINH. Pretty sure what's going on is that FPSINH has been handed an ordinary float argument instead of a bigfloat. I'm guessing related functions could have the same bug.