Should error message in my UI be sticky (shown again on orientation change) or one-off events? Is it correct to say that one-off actions (i.e. suspending functions) should show one-off error messages (like a failed login attempt) and failed Flows (like a list not being able to load because of insufficient permissions) should show a sticky error message?

Not a designer, but: it depends on the type of error. If it's an error you want displayed until the user dismisses it, it would make sense to have it persist configuration changes.

makes sense