The log_abs_det_jacobian 7 in the SigmoidTransform, is implemented as
-(y.reciprocal() + (1 - y).reciprocal()).log()

but I think the correct implementation should be
-(y.reciprocal().log() + (1 - y).reciprocal().log())

or even simpler y.log() + (1-y).log() since log(a) + log(b) does not equal to log(a + b).