DW3000 ranging not reliable

I am first to write this forum.
I am trying to measure angle and distance of the Tag relative to two known Anchor positions using dw3000 module from here.

I first tried to measure distance using code from here

however the output is not reliable even within 50cm distance with LOS.
The least latency I could get was about 500ms and it stops getting distance for no apparent reason.
They all powered from a USB port.
Is there a way to improve reliability of the connection?
Any suggestions would be much appreciated.