It’s a bit difficult to explain, I will try to do it.
Your character in the loading screen seems that is actually already active.
I don’t know if he can move clicking randomly with mouse because obviously I can’t see him.
I’m talking about a few seconds in the loading screen, maybe 4 or 5 seconds.
Anyway I accidentally pressed Esc key and I heard the sound of opening menu.
Same thing for the inventory but…I was in the loading screen.
Suddenly I…heard my character’s screams and after the loading screen finished I saw that my character had half life and was surrounded by mobs demons and so on.
After a few sec of “panic attack” (I pressed all the keys on the keyboard 
) I started attacking mobs and I survived.
Has this happened to you? Is this a problem that can be solved?
This is the weirdest thing I’ve ever seen in an online arpg but I think there is a “technical explanation” which I obviously don’t know.
EDIT: I forgot to write that when the loading screen ended and I went back to the game the game seemed to “lag” for a while (1 sec).
I don’t want to use wrong terms but I think it’s a “synchronization issue” between you and the server? Something like that?