As indicated by sounds, or your ability to interact (reported as a separate bug) with the game before the loading screen finally disappears, the game isn't frozen. This is not alright as some process may resume while the player isn't able to play yet.
No, I'm a Human who have to reproduce you're tickets.
There's nothing to reproduce for me, so we need your output_log to investigate it further
After talking at length with the code team I can confirm that this issue is not fixable. It's the result of a long standing issue in the loading process (a lesson well learned for our next title) and fixing it is highly liable to cause further issues in other core mechanics.
We've determined that fixing this issue would cost too much time for the impact it has on gameplay.
It's likely this is more noticeable now due to another issue that was addressed previously: http://brightrockgames.userecho.com/topics/39-loading-a-save-causes-all-units-to-freeze-until-the-game-initializes-fully/
Apologies that we cannot address this issue.
As an aside including all the additional information can be highly fruitful, especially if volunteers or our team are struggling to replicate. We can get a surprising amount of info from output logs. :)
Why you can't pause-unpause the game though like the user can when he opens the menu?
Honestly it's a bit above my head. But my presumption is that it would affect the process of initializing the level and thus would have the impact I stipulated above.
Please upload output_log when such a thing happens agin, then the coders can take a look at it.
Thanky you :)