was unnecessary because the [*Kepler*]{} observations showed that the TTV planets regularly have almost circular orbits.

There were various hiccups while the code was being developed and tested. Some were more serious than others. In most cases, I was able to link these problematic cases to systems that were too compact, too close to resonances or something else, but sometimes a perfectly normal system was giving me a trouble. After weeks and weeks of struggle, with the problem seemingly going away and then coming back when I least expected it, I started to suspect that the Fourier expansion of the potential is at fault. I have adapted this part of the code from another program that was given to me by my former teacher and advisor, Miloš Šidlichovský, who developed and used it for other projects.

It took some courage to start suspecting that something funky is going on in that part of the code, because Miloš is a very careful man. I would rather expect to find a bug in my code. Tracking the issue down, however, I found that some coefficients of the expansion are exactly two times smaller than they should be, and applied an empirical patch 