@esch5995 wrote:
Have you tried clicking the Blue Stop Icon that appears when you select the upgrade? I have often wondered if this would stop the upgrade process, but since that is not my goal and so much is not documented in this game I don't want to test it myself.
The "blue stop icon" as you call it only changes the upgrade to another building and causes a 30 min delay in the building you clicked on to be available to upgrade again. It does not prevent it from having an upgrade (yellow hat) icon again, but you will have a blue timer icon above the building until the 30 minutes is up.
I have used it many times when there is a specific building I want to upgrade and I use the "blue stop icon" until the upgrade moves the building I want.