XBee S8 module data missing

I am from India.
Using Xbee S8 module (865/868LP).

The firmware version is: 8076
Channel Mask is: 0x1FF (863 to 865) even tried with 0x3FFFFFFF
Transmit power level: 25mV
Encryption: Enabled

When I did the throughput testing putting both the devices beside I got around 16 kbps throughput, but when I did the testing while keeping the devices 50 meters away with a minor obstacle like 1 wall then data packet missing started.

Why it is happening in just only 50 meters?

https://www.digi.com/support/knowledge-base/maximizing-range

It is the obstructions that absorb some of the energy and cause the packets to be loss.