Linking dependencies between tasks in different epics in Timeline

[Pete Woolley]

I can drag links between epics to epics, epics to tasks (in different epics), but I don't seem to be able to link tasks to tasks in different epics (in the same project) - Jira shows an error saying to remove the existing link between the two of them first - which doesn't exist:

As you can see, no current link:

Is there a restriction in place to link tasks to tasks in different epics? Linking tasks to tasks inside the same epic is working fine.