[Q] Not recognizing the current volume level unless adjusted

My tab (P4wifi model) does not seem to recognize the current volume level when I start playing any app with sound (Youtube, Netflix etc.).
The moment I adjust the volume up or down (physical button or on screen), volume comes back up and from there it acts normally.
For example, if the volume level by default is 80% and if I start playing something on Netflix, it plays in very low volume and then if I reduce/increase the volume even just by 1, then sound comes back up to the actual level as if it never knew the volume was 80%.

I have tried many Roms like cyanogen, SGT7, Omni 4.4, Nameless 4.4 and now I'm on SlimSaber 4.3.1. As far as I can remember, it used to work fine in stock ROM and somehow broke somewhere along the way.
I am not able to figure out what I did wrong and not able to figure out an exact match for the problem even after searching posts here. I know this tab generally lacks volume and also about multiple apps to boost (ViperFx etc) this. But, I am fine with how loud this tablet is. But not the way it behaves when starting up an app with sound.

If this is a hardware problem, I don't know how everything works normal when I adjust the volume even by a little bit. Any help is appreciated.

Thank you. I will try that tonight and see what happens.

Okay so, I went back to Stock 4.0.4 and tested YouTube volume. No problems there. Couldn't test Netflix as it wasn't showing up on play store.

Now, I switched back to SlimSaber 4.3.1 by restoring a nandroid back up with TWRP. Same original issue with volume still exist.

One thing I noticed during the first boot to SlimSaber ROM was the media volume setting was always showing lowest (silent) and wasn't saving the setting even after changing it multiple times. But, this problem got sorted out on its own after a reboot.

I had tried flashing the ROM before restoring backup like you said in your reply. But, at that time ROM did not boot due to some issue. It was stuck at SlimSaber logo. I'm going to try this couple of more times during the weekend and will flash the ROM instead of restoring nandroid to see if that makes any difference.