Recording noise issues even after replacing unit

Hi there - I first started noticing recording issues when sending audios via WhatsApp - high-pitched noises like microphone feedback. At first, it didn't always happen but then it became more frequent to the point it is now useless.

I replaced the charging unit which also has the microphone and the problem persists.

Some other notes:

- When using the LG HD Recorder, if I connect my earphones and use Concert mode, the earphones are used for monitoring and the noise is present even when not recording.

- When recording videos in different modes, seems a bit random when it happens.

- Phone calls are working normally.

- I already did a reset to factory

Is there any other hardware that can be at fault? I noticed Witrigs has another mic listed (https://www.witrigs.com/oem-microphone-f...) and I believe this phones uses other ways of recording on certain modes. The fact that calls are working properly makes me thing there's something else to be replaced.

On another note, as I was going to open my phone, decided to try my luck with a battery replacement - everything worked well with that however now there's a white-greenish line and a pink one across the screen, from top to bottom. Already checked the screen flex cable and it doesn't look like it was damaged. Anything else I can do or now the display unit is also damaged?

Maybe it's time to retire this phone :/

Thank you in advance for any help.