I would try:

Manually download the previous version from https://hub.safe.com/publishers/safe/packages/s3connector

Remove newer package from desktop and server, install previous again.

Thank, @nielsgerrits​ !

Is there a smart way to remove packages in a structured way from FME Server? It seems that the package is split up into different folders...

I don't know to be honest, never tried, but I know you can download previous versions from the hub.

Personally, I would just try, it is not working now so you can't break anything. :)

@nielsgerrits​  I tried but it didn't work. So I removed the package-items manually and tried re-uploading but nothing happens. And the panic is rapidly increasing...

Then you need to contact your reseller or safe software's helpdesk I'm afraid.

What a strange problem. I finally managed to upload the package correctly. I don't know if it was due to the fact that I removed some items manually or if there was a mismatch between my Transformer and my FME Package. I must say the setup is a bit too complicated for me, with web connection, web service and fme package... Anyways, I'm a happy camper now. And thanks again for your input and interest, @nielsgerrits​