I had hoped, for a brief moment, that my elongated star were the result of guiding problem. I made a short video of my aligned subs on NGC 3628, and that gave me some prospect that the optical train were not tilted.

Alas, it was short lived. I made a few tests to examine the diffraction spikes, and as you can see in the image above, and also here and here, there is a double-spike mishap.

The waiting game continues, until the next time the problem can be troubleshooted.