This only happens in single-player mode. In multiplayer mode, the technology window closes and the research starts properly.
My guess is that this bug is caused by this bugfix in 0.12.14:
Are you checking if the game is paused, perhaps? In single-player mode, the game is paused when the technology window is open!- Some ui actions made while the game was being saved were actually not executed altough it looked like it.
(https://forums.factorio.com/forum/vie ... hp?t=16866)