The minimum chunk sizes recommendation for the OSS resumable endpoint(s) is a recommendation is 5MB ( and in certain cases, maybe adjusted to be no lower than 2MB in chunk size ).
However, we were not enforcing until now. We will be making changes to OSS to enforce a minimum chunk size ( 2MB chunks ) but we are still recommending a 5MB or greater chunk size.
Only the last chunk (identified by range covering the last byte in the total bytes of the object) will be allowed to be smaller than the 2MB limit.