When there are special chars (`|`, `<`, `#`, etc) present in the path, clicking "+" have no effect. This can happen on matrix test report page in case axes/values contain any such characters. The same will likely happen when present in test case/method name.

The relative path to the test report is used as html element ID fragments. These IDs are passed unescaped into javascript handler so it is looking up the unescaped variants.