The loading icon is displayed whenever the client thinks there are open connections to the XAS.
Every call to the XAS is tracked by the client and when a call returns, the client checks to see if there are any other open calls left. If not, it removes the icon.
This should happen regardless of validation errors, etc.
It also doesn't happen with long running background microflows - no connection is kept open for this. (The client will periodically poll for status, which, again temporarily triggers the loading icon for the duration of the polling call).
So in the normal course of events you should never see the loading icon running without having corresponding open calls to the XAS in Firebug. So, all-in-all this would seem to indicate that you have encountered a bug (between the call handoff from the host to the client). If you can reproduce this in a test project and submit it as a bug in MXDN, I would be most grateful.
After migrating to 126.96.36.199 i've noticed that the loading icon is never visible. Some of our microflows in 2441 were triggering the loading icon but after migration we can't see the loading icon. So what does this mean?