some 3D illustrations being rejected

Lately I have been uploading and selling a number of 3D illustrations I created.  They are all created using the exact same settings and quality. Until the last week,  were accepted and my sales have been pretty good on them.  of the last 12 submissions, 8 were accepted and 4 were rejected saying the quality isn't acceptable. These are not photographs where its very possible randomg quality issues may happen.  These are digitally created, realistic looking graphic assets that are set the render in exactly the same quality levels. I'm not a noob at creating graphics so I do understand what I'm doing. Is this a case of the peple reviewing files uploaded not knowing what they are doing or maybe using photographic standards to review digital illustrations? 

It's very frustrating and feeling like I should use a different site to sell these files on.

Any suggestions?