The service that I work on interfaces with things that other people work on. One problem that came up multiple times is that these other systems have hard-coded invalid assumptions that have worked so far, for various reasons. One of the reasons is that one of the early features that didn't fit those assumptions simply got reclassified as unsupported and has been removed from every release. Due to these problems, I'll have to account for these hard-coded assumptions in these other systems when adding new features in the future.