I'm suffering extended delay when I successfully end the mission (before the Mission End screen appears).
In V18 Steam stable, it happened only occasionally and the delay lasted for about 10 seconds after my final move and the screen appearing. Now in Experimental, it happened to me each time, and the delay was between about 30 and 60 seconds. It's nothing major, but it's a real nuisance.
Also, after I ended my move and after the NPCs have moved (the Hidden Movement screens are all gone and there's nothing going on movement- and sound-wise anymore), there's a delay of a couple of seconds before I'm able to move. The screen is already scrolled to center my activated soldier, but the AP are still visibly reduced in all the mini-stat-displays from the last move. After 1 to 3 seconds or so, the AP visibly fill up and then I'm able to act. This wasn't the case with the stable build, either.
I can't say if the 2 delays are related, tho.