Does switching to a slightly different zoom level restore visibility to the partially vanished links ?

( This bug, and the family of OmniGraffle screen display bugs to which it is related, seem to be rooted in a misfired attempt to improve screen speed by skipping certain kinds of 'unnecessary' display updates ...

Typically, the zoom level in which the error first occurred remains corrupted (data or recent edits partially invisible or misrepresented), but other zoom levels may fully display the data in its correct and current editing state).

[A conversation with support some weeks ago suggested that the chances of Omni actually fixing it before another major version is developed seem to be rather slim.]