I hope someone didn't already mentionned it.

I use the last patch (Elemental Beta 1 Update (0.22.011 on Impulse))

In the technology screen, If I drag a technology and dropping on the other one then taking the previous one and dropping again,then taking > dropping, taking > dropping, ... then the technology disappear

So, If I have Warfare and Civilization.

>I drag Warfare on the bottom

>then I click on Civilization and dragging it to the bottom -this war Warfare is replaced by Civilization-

>then taking again Warfare and dropping on Civilization

>then taking again Civilization and dropping on Warfare...

etc...

after a while, I have one technology who dissapear

Not sure if everybody understand what I'm trying to explain ( (english is not my main language  and the video thingy from jing doesn't work for me)

Here is a screenshot :