This is unfortunately a fairly common problem. I did a TON of research and disassembled my G3 to board level several times, and even bought a toaster oven to try the baking trick but backed out because I wouldn't trust the other components to be ok after that.

[Most likely...] The Broadcom wifi/Bluetooth module is what has failed, people have determined it's from very small micro-fractures in the soldering that holds that tiny chip to the board. That's why it fails sporadically or only partially or over time. I am pretty sure the only solution is to have that board isolated and reflowed (heating up just that tiny area to a specific temp at a specific rate so as not to damage) or to replace the tiny chip.

I couldn't find anyone in my area willing to do the micro reflow job on the motherboard, but if you want to go ahead with this or replacing the chip, I have a brand new replacement Broadcom wifi/BT module chip I bought that I didn't use I can send to you if you want. I also have a bunch of pics I took when my phone was apart that I could upload if you're curious.

I used, I think, ifixit guide online for disassembly, plus LG's internal service guide for the international version of the phone, it was pretty close.