Xperia Z3 Plus, Inconsistent Media Volume or Auto Optimization

[Sylus]

Hello

Bought this extremely awesome phone which is good in every aspects except the Speaker. While playing Music with Sony's own app or watching any video, the sound (tone) changes.To restore the perfect tone I need to stop the music, remove from recent apps, open it again and its restored for maybe 10 secs(very inconsistent timing) and back to same distorted tone. I've tried clearing data, repairing, taking it service center and still no fix.Service center executives refuse to believe that such problems exists. My only Question is If this is a Hardware issue or a software bug. And no water contact has been made till date. I'm not sure but I think the problem was also on Lollipop. Love this phone though! 

Thankyou

[Uliwooly]

@Sylus

What do you mean that the tone changes?

[Sylus]

Sound looses lot's of bass and the vocals are all muddled up. It's almost like connecting an old pair of headphones half way through so you only get one channel of the headphones working and no thump or bass. But both speakers work in stereo. Another closest example would be toggling On/Off S-Force Front Surround while music is playing. It slightly resembles my issue.

[Uliwooly]

@Sylus

Could you test it on safe mode ?

[Sylus]

Yea, that's been done.

[Uliwooly]

@Sylus

Do you experience the same while on safe mode?

[Sylus]

Still the same in Safe Mode.

[Uliwooly]

@Sylus

That's quite odd, any suggestions @alexdon

[_alexdon_]

@Sylus Have you tried clearing data for music app under settings - apps - all? Also, you say you can replicate the issue?

[Sylus]

I've rest/repaired my phone 4 times now and cleared the data also. My issue sound like turning off/on S Force Surround. That tone change is irritating.