From it seems it is possible for an in-progress Synapse multi part upload state to be inconsistent with an S3 multi part upload state which is either completed or aborted. As a result any upload attempt will fail, e.g.
We should catch this case and automatically reset the upload with a forceRetry.
Originally observed on the below but not specific to the below and will reproduce through version 2.1.0
synapseclient version is 1.9.4
Red Hat Enterprise Linux Server release 6.10 (Santiago)