Sporadic failures in an iPhone SE

I'll preface this with some info here;

Sftwre V: 13.1.3

M/N: NP822ZP/A

Never Jailbroken, or otherwise modified outside of warranty conditions.

Max Batt. Cap.: 82% (Optimised Battery Charging - ON)

I have recently been plagued with a few issues on my (admittedly ageing) iPhone SE NP822ZP/A.

I'll list these out below with as much detail and information as possible to see if there is anything I can do before biting the bullet and going to an actual apple vendor to have them tell me to upgrade.

Note: All issues have been present since the roll-out of IOS 13, and have persisted through the various patches and hot-fixes Apple has release since. Battery problems have been apparent from prior to IOS 13.

Random shutdowns of whole phone at or below 30% battery:

Commonplace at ~12-13% charge. Operating temperatures are NOT a factor here, all times are in environments at or frankly below room temperature, in a thin case.

Sporadic crashing of Apple Music client:

The music client will not function, and the control center applet for Music will just disappear until restart of iPhone.

Volume control issues:

Immediately after restart or prolonged sleep of device, for approximately two to three minutes, the volume controls, either physical or digital, will not function. Not inputs are registered or carried out by the device, with Bluetooth headphones, wired headphones, or just with speakers. That is, until two to three minutes later when every single volume control input is carried out with the exact timing of when you pressed the controls two to three minutes earlier. No further control inputs are accepted until the "queued" actions are completed, then action returns to normal.

I would love to give crash reports, and further information, maybe debug info but this is an Apple device, and I don't have access to that.

Suggestions, perhaps referral to support team? Apparently my device is not eligible for tech support via Apple Support chat.

Cheers.