Hey @nrs.andrew,
Thank you for reporting this bug. We have taken note of this and are working on pushing a fix. The Status will be updated on this post once fixed.
@nrs.andrew The onSuccess fallback method gets executed as the last step in the upload process. If there is an error in that then the upload would fail. Can you please show us the code you are trying to execute in the fallback function?
We looked at your code and noticed one problem. Keys have to have 0x prepended to them. Can you please make this change and see if that resolves the issue.
We will be pushing out a fix in the upcoming release to ensure that keys come prepended with 0x so that it won’t be necessary for the developer to do this in the future.