It seems to take a long time to load the VTB for Agile board > Sprint Tracking > Task board
Depending on the amount of Swimlanes on your VTB, this performance hit is expected.
Upon review by our Development team, it was mentioned that a performance hit would be expected due to a high amount of Swimlanes on the Visual Task Board.
The Visual Task Board on the affected instance had 83 Swimlanes. Development has mentioned that if there are more than 50 Swimlanes then it will take 20+ seconds to load.
For normal performance, there would need to not be more than 20 Swimlanes.