Android Question Android device ID changes

[Rusty]

I have been using Erel's tutorial example here to create unique ID's for each of the deployed devices.
Since Ice Cream Sandwich until now (Lollipop/Marshmallow API 21 or greater), the ID has always been reliable using Erel's code.
Now, on occasion and not always, the code changes...

i.e.
Original ID: F7NPFP104877 (supposedly the device Serial number)
Today's ID: 6dad8f6677713ad9 (looks Hex to me)

This "seems" to happen only on API 21 or greater tablets, but since it is not occurring on all devices, it could happen (I assume) on any API.
So far, the only place this is happening is on API 21 tablets.
Any advice on resolving this will be greatly appreciated.
Rusty

 

[Erel]

It is not expected to change. It is a hardware serial number: http://developer.android.com/intl/es/reference/android/os/Build.html#SERIAL

 

[Rusty]

Thanks Erel,
Any idea why it is changing? I'm using the exact code from the tutorial.
I think I may need to change to MAC address, I'm pretty sure that's unique and unchangeable.
Your thoughts?
Rusty

 

[Erel]

No idea. There are examples in the forum that show how to get the mac address. Note that you cannot get the mac address on Android 6+.

 

[somed3v3loper]

It is not expected to change. It is a hardware serial number: http://developer.android.com/intl/es/reference/android/os/Build.html#SERIAL

I think I have seen some Xposed modules or Root Apps (Don't remember ) that claim to change device ID .
I did not try them so I am not sure if they work or not .