Bluetooth RSSI and it's fluctuation

[zephrr]

I am using ESP32 RSSI to estimate the distance between beacon and receiver for asset tracking. I am using 3 receiver and 1 beacon (Tag) all of them being ESP32 and using Bluetooth RSSI detected by the receivers to estimate the distance of beacon with respect to each reciever to estimate the position of beacon and track it.

However, the RSSI captured of the beacon with respect to each receiver fluctuates a lot. Like if i note the RSSI of the beacon at a given position with respect to a receiver it won't be the same RSSI at the same position if i move around before placing it there again.

Do anyone have any idea why this is the case or if i should change the receiver or beacon with a better beacon for bluetooth or a better receiver for capturing RSSI, if the issue is that ESP32 Bluetooth is because of heat of the CPU?