Hi, interesting thread.
@Pytha, about the X3 cam, i have camera who look like excately same, 100% same plastic box same Xdv software,
W60 4K from banggood. I have problems with this cam as it can't record more than 18 secondes with 1080P 60fps and only with high light condition, in low light it can record more, same with 720P but 37 seconds, no more. No problem to record in false 4K 30fps.
I have tried many different micro sd, all class 10 minimum.
I have done many videos to test it, tried many differents parameters nothing change. But what i have seen is that video size in 4K and 2.7K aren't true 4K/2.7K. It is said as 30fps, but 4k 30fps is obviously not true 30 fps by only watching video fluidity.
I have opened it and see that chipset is allwinner V3 (i read that this chipset isn't able to do 4k 30fps), like elephone ele cam and like your X3 cam (i guess X3 has Allwinner chipset also). I have tried to find fireware without success and i don' know if Eken firmware can works on this camera.
Photo quality are horrible. Wrote on the box : effective pixel, 16M, 12M.... lol
So this camera, as lot of cheap cam, have wrong specifications, but worst, doesn't even works ^^
I hope i'm not too much off topic with my post.