Venus speed - small irregularities in the planetary motion

Have you ever been interested to know how Venus speed changes in time? Look at this diagram for Venus speed:

The negative zones of this diagram represent the periods when Venus is retrograde, while positive zones are the periods when Venus is direct.

If Venus is direct, it moves a significant period of time (about one year) practically with the same speed (it is just a bit faster than one degree per day).

However, if we look at this period more attentively, we find small irregularities in Venus motion: from time to time Venus decreases and increases its speed, and this may happen several times per month. Here are these irregular zones (they are  marked by vertical stripes):

Why do these irregularities appear? Is this a bug in the program?

No, it is not; the program works ok. These irregularities in Venus motion are caused by a small oscillation of the Ecliptic plane caused by the Moon movement. Thus these irregularities represent the effect of the Moon tidal force which oscillates the Ecliptic, and finally we observe this effect as irregularities in Venus speed.

BTW, this Lunar effect is especially strong if you analyze the ACCELERATION of Venus, here it is (together with the Mon phases):