I hit a rather confusing issue with a release a while back, which initially appeared to be a Unicorn problem. But after investigating the details, I think this was actually an infrastructure problem causing some odd behaviour. I doubt this is a common problem, but still worth writing down in case it's a challenge for anyone else...
My QA team had a deployment issue recently, where Azure DevOps failed to successfully release to a couple of servers. The reason for the failure wasn't obvious to me immediately, so here's a quick write-up for Google, in the hope it saves some other people.
I was creating a quick package to transfer some content between Sitecore instances the other day, and happened to scroll down to the bottom of the Metadata page in Package Designer. Not for any real reason – just some over-enthusiastic scroll-wheel action. But when I looked at the dialog, it struck me that there were two fields here I'd never paid any attention to before: