Hi,
this seems to be caused by a rounding error - I'm not exactly sure which part is to blame, but
this line defines a precision of 10 for all values to be tested, while
this test case has values all over the place, ranging from six to eleven digits after the decimal point.
If you are just trying to use plus codes, it is probably safe to just remove that ultra-exact test case for the time being. If you want to contribute code, it might be worth checking out why this test fails for you but apparently not on GitHub - I'm not a Python expert, so can't really help with that part. :)