Duplicate key values in #switch ({{ #switch: {{{param}}} | a = apple | b = banana | a = apricot }}) are silently ignored, with only the first duplicate branch followed (param=a results in apple). Currently, this is not tracked in any way, meaning it has to be spotted manually. It'd be nice if there was a tracking mechanism (some combination of tracking category, error message, linting category, etc) to allow these to be found and fixed more easily.