woofer excursion at start of lp

Another possibility. Isolation.
Given all your geometries are correct....
I noticed you are using an Ikea shelf, which is hollow. And your right speaker is relatively close to your turntable. I think you may be getting some kind of feedback.
My Mississippi River Rig has a Rega turntable on the same Ikea Expedit shelf and I was having the same issue. I was able to eliminate the problem by placing Vibrapods under the turntable feet. Sometimes rigid points are good isolators, sometimes sorborthane or some such softer system. In my case the softer footer did the trick on the Ikea. Might work for you too. Good luck.
Dave

There is always more woofer excursion due to record warping which is more present at the beginning than at the end of the record. You probably also have an amplification system which is able to amplify linearly very low frequencies, maybe even DC, which will make the phenomenon more pronounced and visible on the woofer cones. See if you have any kind of high-pass, or capacitor coupling option somewhere on your audio components. If you have one, you can use it in order to attenuate the problem.

Another option.
If the excursion occurs as the volume is increased, and
if it is some sort of airborn feedback resulting from speaker/table interaction,
another easy solution could be moving your speaker either into the room or to the right. Of course you'd need to adjust both your speaker positions to "dial" them in.....