“Pretty consistent” and “deterministic” are not at all the same
It's close but not fully deterministic. I remember seeing a theory that if the system is considering multiple possible completions that have the same rounded score percentage, then its choice between them is nondeterministic.
It's likely because GPU calculations are non-deterministic and small differences in floating point numbers could lead to different outcomes (either in the way you described or somewhere deeper in the model)
> GPU calculations are non-deterministic
Tensorflow is non-deterministic for some operations due to thread scheduling. PyTorch doesn’t have this issue.