This seems to be a serious bug of SwiftUIs Charts API. In case there are several Chart-Views generated inside a ForEach-Loop the Chart-Views sometimes do not match the data of the relevant loop-run anymore. This bug appears especially as soon as the view was updated by the OS (e.g. switching tabs, scrolling, ...), not so often when the view was generated initially. This bug appeared with one of the latest OS Updates (iOS, iPadOS, macOS). I can't see any misuse here. I also couldn't find a workaround. I recommend reporting this to Apple.

Maybe, it's not a bug and I found the solution: Use .id() with Charts, e.g. Chart {...}.id(someHashableObject) Pseudocode example: ForEach (identifiableObjects) { identifiableObject in Chart { // some Marks... } .id(UUID()) } Seems to work in my case.