Ben,
Don’t know whether you got your issue squared away but I had a similar issue and this is what worked for me: Remove the S3 source (the connection, not the PDS) and readd. I know this can be a pain if you already have a lot of PDSes defined on that connection, but that did it for me. The fact that this is what cleared it up for me makes me think that the metadata is being cached on the executor but the refresh is only being executed on the master. Anyway, hope this helps.
Thanks,
Chip