HoughLines minTheta / maxTheta have strange behavior

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I'm working with an image with some lines at 6~10 degrees. So, I decided to use HoughLines to detect those lines, limiting the search angle to that range. However, the outcome of changing those two parameters are really not behaving as I expected.

lines = cv2.HoughLines(borders, 0.5, np.radians(0.01), 100, min_theta=np.radians(2), max_theta=np.radians(10)) finds 55 lines with angles between 7 and 8 degrees. Changing min_theta to np.radians(3) finds 0 lines.

Also, sometimes HoughLines finds lines with angle exactly 0. That's especially common when the threshold is low and is obviously outside the range [min_theta, max_theta].

Is there something I'm missing about the use of these two arguments?