A weird hardware problem

[p1114501510]

Hi, everyone. One of my friends has designed a 60% keyboard based on the design of GH60 Rev B. He added full RGB lights which are controlled by PCA9635. Now, the weird problem is the usb connection is extremely unstable. The connection can only last 5 minutes. That's quite annoying.  However, the second 32u4 which controlls PCA9635 is just fine. The connection is very stable. My friends and I have checked the hardware for more than two days and still cannot find any hardware errors. I have the schematic of the pcb. Can anyone tell me what's wrong with that? Thx a lot.

[senso]

Both USB VCC are shared, so the lowest resistance connection is the one that will feed everything, I smell that its going way over the 500mA limit and the port gets disconnected.
Or maybe the fact that the USB lines jump over vias a couple of times and run all across the board without a ground plane.
Also, are the USB D+ and D- from both micros really connected in the W1 and W2 jumpers?!

[p1114501510]

Thx a lot, I pmed you about my problems.