[Question] Lenovo K3 Note Speaker Issue

[riad]

I'm using Lenovo K3 Note(K50-T5) for 2 months.
Everything was fine.
But,from yesterday I'm facing sound decreasing issue.
If I play music/video more than 25-30 minutes, the loudspeker sound automatically decreased.
But,volume level isn't decreasing.
If I reboot my device, the problem is solved for a few time.
After 25-30 minutes the same problem happens again.
I've tried formatting my device using sp tool & installed the stock firmware again.
But, I'm still facing the problem .
I think it's hardware issue,is it??
is there anyone, having experience about this issue?

[modestMouse]

This could be hardware, or software.

If you've done any recent OTA updates, they may have made changes. Did you revert to your original ROM and see if the problem is still there?

Also, if you haven't updated, then try to update to the latest ROM and see if the problem still exists.