Oooh, that’s weird.
Now we have someone saying “don’t use Gunzip module” in an older thread here:
Update… I turfed the GUNZIP module and am using the Convert Encoding module. It outputs a single line text which is converted into a table if the header is ignored.
– Amazon Seller Central - GUNZIP Error - #17 by Ricardo_da_Costa
And now you’re saying Gunzip works with the same “Download a Report Document”.
The only difference I can see is one contains JSON data, and yours is CSV data.
So Amazon might be applying GZIP compression to only the CSV downloads.