WE G19 Double trigger click
 

I noticed that pressing the trigger of my WE G19 does a small "click" before firing. Detaching the slide I can se that when I hear this first little click the end of the trigger bar sticking out the hammer housing moves a little.
No a real problem for now and if I press the trigger quickly the issue is not so obvious.
Is it normal in this kind of pistol or may be the start of a real issue?

It's normal for WE Glocks because they designed their hammer housing that way, with an extra "jagged“edge, so the trigger stay on the back, after a dry fire/last round, till you pull the slide.
Airsoft Glocks that I know will do that: (different batches may vary).
Most (if not all) WE Glocks, excluding HK3P Glocks
TM G17
Bell G17
Army G17
Stark Arms G18

Airsoft Glocks that I know will NOT do that: (different batches may vary).
KJW G23
Some HK3P G17

If you look this video (German suntitled English) https://www.youtube.com/watch?v=4-lQQDVCpjc at 06.35 I seems that the trigger makes 1 click only

The Video actually shows the trigger making 2 clicks.
http://airsoftcanada.com/picture.php...pictureid=6854
This is the first click, notice how he let the trigger stops there for a while, and we can hear a small click in the audio.
On some indiviual guns the "click" is very noticeable, on some the click is rather small and it feels more like a sudden increase on the trigger force, passing the "click point", like a 2-stage trigger.

http://airsoftcanada.com/picture.php...pictureid=6855
This is after the second click, the hammer already hit (we heard a loud click in video).

Ok, you are right, I turned up audio and I heared 2 clicks!!!