"Link diagrams navigation" moves diagram not far enough

Reproduce:

• In Cockpit EE, goto Migration page and select two diagrams to display
• ensure that "link diagrams navigation" is checked
• move the left diagram

Expected:

• the right diagram is moved the exact same distance as the left diagram

Observed:

• the right diagram is moved a shorter distance
• The diagram that is dragged is always moved more than the linked diagram