Streamed audio content low pitched, VOIP high pitched - local files ok

I replaced the main board in my overheating S6 Edge G928i 32GB with a board from a 64GB G928C (same as F model). Went swell, no more overheating.. but it has a bizarre problem, the pitch of audio not stored locally is like a horror movies, super low pitch deep boomy slow motion sounding. Yet if I make a Viber/Skype/Whats App VOIP call, the other person hears me in a super high pitched mickey mouse voice.

Low pitch/slow motion sound:

- Streaming over Youtube, Spotify, distorted as above (slow motion/lower pitch sound)

- TTS (Google Maps driving, Sygic GPS instructions) as above, low pitch

High pitched/super fast sound:

- How other people hear me over VOIP apps (anything with a voice out) not NOT normal phone calls over telephone network.

However if I copy a video to onboard memory or record a video all fine and playback from Gallery etc its just fine.

I've swapped wiring, microphone and other bits between the two phones. I've reset the phone to factory. I've upgraded to Android 7.0. Ive rooted the phone... no change aside from the fact it sometimes works ok but usually just happens shortly again and stays that way for ages. I'm near positive this is a hardware problem in some manner.. ideas?