Using the SNAP 11-SNAPSHOT (from end of last week) there is an issue with the decode qualification.
For a zipped ZNAP file also the Sentinel-3 reader plugin says it is applicable.
Probably the check is not specific enough.
Jira ticket SNAP-3769 created
Marco,
can you please send the product name that triggered this duplicate reader request.
Thanks,
Tom
This is the product: