I’ve noticed this happening in versions 5 and 6: you can try opening the example project, set the line annotation „ROTATING-TEST“ to “rotated”, then reload the project – it will always reset from “rotated” to “axis aligned”
I regularly use some custom created lines that use rotated symbols, like the damping mark I mocked-up for the sample project: but I always have to remember reassigning this “rotated” property for all the custom elements when reloading a project…
rotate-test.dorico (1.6 MB)