Hi,
Here is a link to the Ifixit guide to teardown a Lg G5.
At step 14 in the guide it shows the placement of the WiFi/BT controller chip, highlighted in a red box. As there are no obvious antenna connections nearby and the complete parts teardown doesn't show any separate antenna leads, I suspect that the antenna(s) are most probably coils mounted on the board itself. If this is correct either one of the coils is loose or the controller chip's section for 2.4GHz is faulty. BT operates on the same frequency so it would use the same antenna.
[guide|61205]