Guys, I have the same issue and I solve it my self already. It happend to my Kunai 3 on ROG phone 2 often disconnected and can't update right side of the controller cause failed every time.
After see all the reply, i try to solve ir my self and it work.
First, you need small screwdriver, isopropyl alcohol, small brush, and tissue.
Second, unscrew the phone holder on the side, all 3 screw every side and open it carefully.
As in my screen shot
Third, spay or apply small amount of isopropyl alcohol on the contact copper and clean it using brush. (note: the brush must be dry and clean otherwise it's just make it worst). And clean the copper with tissue. Repeat this step at least 3 time.
Fourth, put it back together and see if it connected and seen in hardware information.
Overall, I think it's just connection problem since it can't connected with bad contact plat.
As in my screenshot, it seen right controller version is detected as 3.1.0 not ff.ff.ff and i try to use it for awhile it work properly. Although idk why my system read it as Kunai 2 but at least it work.
