"Mysterious radio signals" - how could a geostationary satellite and Ross-128 line up with Arecibo?
The original team suggested three main possibilities: "(1) unusual stellar activity, (2) emissions from other background objects, or (3) interference from satellite communications"  Clearly radio astronomers know about satellites.

They noted "in the absence of solid information about the signal, most astronomers would think that [radio interference or instrumental failures] would probably be the most likely explanation."

The satellite hypothesis has some problems it "does not yet explain the strong dispersion-like features of the signals (diagonal lines in the [weird] figure [in the question])" But on a balance of probablities this is the most likely explanation.

There are satellites in the region of Ross 128:



Location of Geostationary satellites operating between 4-8 GHz in the same region of the sky as Ross 128 (yellow dot).
Credit: Enriquez et al. (SETI Berkeley), http://seti.berkeley.edu/ross128.pdf 

Your analysis of the location of a satellite, based on the geometry of satellite orbiting over the equator is not supported by this image.

The observers did not claim to have received a SETI signal. Indeed if you look at their original report they note that "aliens" is at the bottom of their possible explanations. The signal looks different from typical satellite bursts. They hoped the signal was astronomical in nature so there may have been a little wishful thinking.

So the most likely explanation is that we are observing multiple reflections from geostationary satellites transmitting on the 4-8 GHz band.

All quotations from the press release from the planetary habitability observatory.