Side stretch of 3d map stop the resolution at 6-7Å


I have more than 80000 particles that look good in 2D classification containing each side views. However, it only can be solved at 6-7Å. If I decrease the threshold in Chimera, the density looks like being stretched vertically. The Azimuth-elevation figure looks like this:

Does anybody come across this similar problem and have any suggestions?

Many thanks!

@wufei This is the posterior precision distribution, not the orientation distribution. What does the orientation distribution look like?

Thank you for noticing. I have added it to my question. I just guess the posterior precision distribution seems unnormal.

Is there symmetry? Or some strong pseudo-symmetry?

Yes, I give the c3 symmetry. In this aspect, there is also a weird phenomenon, that is symmetry doesn’t help the improvement of resolution. Even I don’t give symmetry, I still get the same map with a similar resolution.

Is the initial model aligned with the symmetry axis?