syn17013485 was the table that had Base64 encoded MD5s in synapse when Dwayne and I were debugging the issue with uploads.
Specificlally, filehandle id 47392642 was shared with me.
For a more general validation, Base64 encoded md5 strings will always have a length of 24 characters since all MD5 digests have a size of 128 bits. The base 64 representations of MD5s should also always be padded with 2 equals signs "==" at the end
I think you used the prod endpoint twice. From the python client: