[Android Head-Units] psyko_chewbacca:
Do you have the schematic specifically for the XRC mainboard? If so please share. If not, find it because just saying it is so doesn't make it true. All signs point to the issue being the GL850G USB hub device and here's why:

First contradictory point: Why is this Wifi/BT issue only prevalent on XRC units? If the problem originated from the RTL8723 module itself, you'd see a whole bunch of people talking about this issue. For now, it seems to affect mostly XRC units. That module is widely used on all types of variants.

Second of all, if you've had gone back a bit in the thread, you'd have seen that I asked to probe the voltage supply line when the module is not detected in android and [MENTION=943895]erkme73[/MENTION] was kind enough to supply proof with pictures that the voltage supply is active and at the right value.

Third you speak of +5V supply, it's 3.3V. Check the schematics.

Fourth, on XRC units at least, listing USB devices when the RTL8723 unit is indeed picked up by Android places the module itself behind a USB 2.0 Hub. Guess which hub it is? Yup the GL850G one.

I found out about this in the dmesg output of a full boot cycle, sleep and then wake (with the Wifi/Bt module not being detected after wake).

In the full dmesg output on pastebin, starting at line 734 shows the detection of the problematic USB hub:

[ 2.188848] usb 1-1: New USB device found,[COLOR="Blue"] idVendor=05e3, idProduct=0608[/COLOR]
[ 2.188857] usb 1-1: New USB device strings: Mfr=0, Product=1, SerialNumber=0
[ 2.188865] usb 1-1: Product: USB2.0 Hub
[ 2.189702] hub 1-1:1.0: USB hub found
[ 2.189709] hub found on USB20 port
[ 2.190084] hub 1-1:1.0: 4 ports detected

VendorId:ProductId matches the description: https://devicehunt.com/search/type/usb/vendor/05E3/device/0608

Then, right below that, starting line 757, detection of the Realtek Wifi/BT module

[ 2.942720] usb 1-1.1: New USB device found,[COLOR="Blue"] idVendor=0bda, idProduct=b720[/COLOR]
[ 2.942728] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2.942736] usb 1-1.1: Product: 802.11n WLAN Adapte
[ 2.942743] usb 1-1.1: Manufacturer: Realtek

In case you're not familiar about USB logical addressing, MD725/RTL8723 device(address 1-1.1) is connected through the hub(1-1).

In the same dmesg output, head unit suspends and wake up (line 2258 in pastebin). You can see starting line 2365 that USB detection starts but surprise surprise, USB hub is found but nothing behind it! This is the thing that made me realize the problem isn't the Wifi/Bt module itself but rather the USB hub.

Fifth, there's a software fix that has been found on 4pda concerning this exact issue. Again, it's mentionned in this very thread, just a couple page back. To put it simply, the fix resets the USB hub after a wake event. Magically, the Wifi/BT unit is picked back up.

To conclude, I'd say a fair amount of testing has been done on this issue.

The fact that there is a working software fix that bases it's fundation directly on the assumption that the problem originates from the USB hub is proof enough.

That Hal9k also plans on integrating this software fix in his next ROM..

That recent reports of people receiving updated XRC boards with GL852G IC instead of GL850 and others being told and shown by sellers that the fix involves desoldering the GL850 IC and replacing it with a GL852 also helps solidify our theory.

I'd say the USB hub theory is pretty much the real deal here.

I'm not saying the problem isn't caused by temperature. It's most likely that the cold affects the operability of the GL850 device. Probably because colder voltage regulators usually take more time to stabilize their voltage outputs and the GL850 has issue with this. [MENTION=943895]erkme73[/MENTION] already proved, again in this very thread, that cold units seems to exhibit the issue significantly more often by placing his head unit in a freezer for I don't know how many times.

So to play with your words:

GL850 USB hub is the problem - I read some guessing without valid testing on your part.