AirPods 2 Replacement Units - Uneven Battery Drain and Right Tip drain more around 10%

Hello readers, 

1st visit replacement 

So recently, I got some issues with mics on my AP2 and went to Genius appointment, and got replaced both of my AirPods Left and Right tips.

- Diagnostic > Passed

- Tested mic > Breaking voices and no sound wavelength issues persists

Then I have follow the instructions for Pairing Process

1) forget old connected AP2

2) Charge AP2 via Lightning Cable for approximately for 40 minutes to an hour - update and match the firmwares in background

3) Press and hold pairing button till the white blink led to setup connection to iPhone device

After few round of tries and monitoring, found out that the battery drains unevenly. which for a new replacement unit (Apple Genius claimed that replacement unit provided were a New Unit in different packaging - not in retail packaging and not refurbished repaired unit. so I expected to have defects free hardware).

Before my replacement unit, my AirPods battery were working fine and drain evenly. 

Apps that I use mainly on music and movie playback, no mics activities involved. no mic indicator throughout the monitoring activities. 

2nd visit replacement 

Had setup another with Genius appointment, went through all the diagnostic process and testing. Found that the firmware wasn't properly updated to the same version, to avoid the hassle and issues end up got replacement of the entire units (Airpods2 Left and Right, and Charging Case). repeat on the same steps of Pairing Process and continue monitoring for the issues. 

3rd visit replacement 

Eventually, the issues of uneven battery drain still persists, other issues doesn't surface any as I have been only using for few days. There I go for another Genius appointment to understand and clarify the issues encountered. So the Apple Genius has helped to diagnose and test the AP2, found out that the AirPods Right Tips is faulty on the mic and hence helped to replace the Right unit. with the few Past visits, it doesn't recommend to replace the entire set as previous visits had done so and doesn't resolve the issue. 

so as of few days of monitoring after the third visits, I am still encountering the same issues. and not sure what has caused it. 

Device connected to - iPhone 12 Pro Max iOS 14.7

TLDR:

1. Replacement unit of AirPods 2 doesn't solve the issues of battery drain unevenly. and after few tries and monitoring, it only drain on the R side more around 10%.

2. 2 times of replacement unit of Right Tips has mic issues (tested by Apple Genius). What happened to the Quality Control? or am I that lucky just to get 2 times faulty Right tips?

3. The microphone has set to - Automatic, so I don't think this is the caused of the issue.

4. Could it be iPhone problem?

5. Retail unit doesn't have this problem as I checked with community with the same AirPods 2 and iPhone devices. 

Appreciate if you could have help to enlighten me, on what can I do to troubleshoot the uneven battery drain? or recalibration of battery? all reset workaround I have tried and still no clue. 

ps. sorry for lengthy and unformatted text.

- Wayne