[HocusLocus]

I would be curious about this comment at the OP site from yesterday as a proposed or contributing cause for such a mysterious limit, it does carry a ring of adversity via absurdity. I do remember the early days of gzip encoding, many apps suffered from confusion over transport vs. delivered content-length.

"[cratermoon] I did a bit of testing using curl and found that with -H 'Accept-Encoding: gzip, deflate, br, zstd' the resulting content-length: 6216 matches the gzipped response. However, without that header the result is not compressed and the response is content-length: 22411. The same difference applies to your other site.

"I wonder if whoever emailed you has crossed up their query and whatever tool they are using is mistakenly complaining because it's expecting 22411 bytes and only getting 6216."