Wax LRS currently supports v0.95, v1.0.0, and v1.0.1. We have built a very comprehensive test suite so that we adhere strictly to the Experience API (xAPI) standard. We believe everyone is still working out kinks in their support for v1.0.0, but implementations are usable now.
We have built a shim to support most (almost all in practice) v0.9 compliant xAPI statements by translating them to v0.95 statements. No one should implement any new v0.9 xAPI functionality, because it is so different from v0.95 and v1.0.0 that data compatibility is a major problem.
We try to provide very thorough error responses for malformed or erroneous xAPI statements so if you are having an error, check out the response or view your debugging page in Wax (for monthly plan customers). If you find any issues with our implementation or have any questions about how it all works please open a ticket and we'd be happy to help get it resolved!
You can find the xAPI v1.0.0 documentation on the ADL GitHub page: https://github.com/adlnet/xAPI-Spec/blob/master/xAPI.md