@David-TP hello, Yes indeed reset itself I downloaded 500mb data logged into the modem webpage switched the modem off and back on total data usage is back to zero......

  @David-TP 

Hello,

David, pass this onto your engineer.

TP-Link NX210 v2 UK model.

Firmware build 1.2.0 3.0.0 v60f3.0 Build 250804 Rel.60572n

The UK ISP I'm using is Three UK.

I did find the bug.

I factory reset four times; each time I factory reset, I did a speed test.

Once the speed test finished, I logged into the router webpage and noted down the total data usage (430 MB, 603 MB, 857 MB and 503 MB).

Once I turn the modem on and off.

I log back into the TP-Link webpage, and the total usage data is showing zero again nothing downloaded.

This time I downloaded bigger files over 5GB, - 15GB, rechecked the total data usage and turned the router off and on.

Total data usage is correct, showing the correct amount of total data used; it didn't reset itself back to zero...

I did this test twice and both times worked perfectly.