If your LG G2 phone performs properly, but only you find issues such as audio crackles, sudden appearance and disappearance of the headset icon on your phone when a headset is plugged into the headphone jack, then great chance is that the issues are occurring because the headphone jack of your LG G2 is loose or the receptors got bent. To confirm this, try using your headphone with other set and see if it works. If yes, then be sure that the issue is with your LG G2 microphone only. To fix the LG G2 Mic Not Working Issue And Audio Crackles you need to go to the technician as it requires replacing the headphone jack.
However, to be sure that the reason is only the loose headphone jack or bent receptor, do the following tests before you go to a technician.
Microphone not working:
This happens when the headphone jack receptor is bent or there is not good contact. Now hold the plug strongly to see that microphone and headset both are working or not. If you get a response when hold tightly, then it says that microphone is working only when there is good contact. So the problem is occurring due to lose headphone jack.
Audio normally crackles when you touch the plug that is inserted into the phone. If your headphone jack is loose, then you might touch the plug to check the issue which causes audio crackles.
Appearance and disappearance of Headphone icon
The phone can detect the headphone only when there is good contact. If it is loose, then phone cannot detect and display the headset. So, this sudden appears and disappears also happens due to the same reason, i.e. the lose headphone jack.
So once you are sure that this is the reason, you can fix the LG G2 mic not working issue and audio crackles by going to a technician. They will replace the jack.