No protein features seen in 2D classes but rather some weird rings

Dear cryoSPRAC users:

I’m a beginner to learn and use cryoSPARC version 3.1.0. Recently we collected a dataset on Krios microscope with K3 detector, the data acquisition settings were:
Total dose: 80 e/A^2
Dose per frame : 2.0 e per frame
40 frames/movie
Defocus range: -0.5 to -2.25 um (interval 0.25 um)
Magnification: 130 kx
Pixel Size (Sampling): 0.675A
Exposure time: 2.3 secs
Spherical abberation (Cs): 2.7
Voltage: 300kv

The protein particle is ~170 kDa and has a size of ~60-160 A in diameter, appearing a bent-rod like shape. I chose elliptical blob for the blob picking on a small batch (~10%) of micrographs and used the following parameters:
Minimum particle diameter: 70 A
Maximum particle diameter: 170 A
Turn off Use circular blob
Turn on Use elliptical blob
Other settings were kept as default.

After inspecting the picks, I did particle extraction using the parameters:
Extraction box size (pix): 400
Fourier crop to box size (pix): 320
Other settings were kept as default.

For 2D classification, the parameters were set as:
Number of 2D classes: 200
Number of final full iterations: 2
Number of online-EM iterations: 40
Batchsize per class: 400
Other settings were kept as default.

But the output 2D shapes don’t appear any protein feature but rather some weird rings, as shown in the attached image.

Could anyone please give me some clue? I couldn’t figure out which step/setting I did wrong.