CSI Phase jumping in RT-AC86U

[Navidt]

Hello. I am working on calculating the angle of arrival and departure from a receiving router and transmitting router, respectively. To measure any hardware effects on the signal, I attached the router's ports to a known wired channel and recorded the packets received. Since everything is being transmitted through a wires channel, it is my understanding that the relative phase between received packets on different receivers should be constant, and that is almost what I see. The plot is showing the relative phase of each received packet to Rx 1 and the same transmitter over time.

As you can see, the relative phase seems to jump between two values. In other experiments, I have seen it jump between three values.
To get an idea of what was happening on all subcarriers, I also plotted the relative phase over subcarriers. Here the jumps manifest as different lines, each corresponding to a set of packets:

Is there any explanation for this behavior?