Repro is with GA Zed tagged v1.7.0.

A community zync user was using the Zed lake migration tools and reported the following failure:

This failure was at the step where it attempted to zed load the ZNG dump of the old-format pool to make the new-format pool. Since we knew the expected input was ZNG, they were able to easily work around the problem by adding an explicit -i zng to the zed load. However, since it's Zed's own format, we'd expect we should be able to auto-detect ZNG pretty reliably, so we'd like to better understand what broke here.

Unfortunately, due to the sensitive nature of the data, it could not be shared for us to reproduce the problem ourselves. Thankfully the zed dev dig frames command can be used to show the structure of the ZNG file without revealing its contents. They shared the following output: