I think I figure out how to work around it. apparently if json is newline delimited, it will not throw error. but if it is standard json array format(comma delimited) , it will throw an error if the array size exceeds about 20 items… very strange.
@marvinwu Correct, we only support JSONL for uploads and looks like we have an issue with not returning a useful error message in that case, will open an internal ticket for this.