I feel that it is an impedance matching problem between the distributor and the terminal. If it is really an impedance matching problem, see if there is an impedance regulator at the terminal, or connect a termination resistor.

The phenomena of the two terminals are different. Let's see if the driving ability of the distributor is not good, and the attenuation is too large after a long line. First connect the terminal through the distributor, mainly the one 50 meters away, and try to see if there is any improvement.