Report slow in Workspace - fast if published to any other Workspace. All shared capacity.

[mmace1]

• Everything is on Shared Capacity (i.e. only Power BI Pro licensing). 
• The workspace is using less than 500Mbs in total

Report A:

• Report A in Workspace 1: Suddenly is extremely slow to load visuals. 
• Publish Report A in any other Workspace - it's fast
• Download report and run in PBI Desktop - it's fast
  
  

This has occured once before - deleting the report/dataset and republishing made it fast in Workspace 1 again - but that cost user's their bookmarks etc, so isn't ideal. 

Any idea on troubleshooting this, short of deleting and republishing?