Why would an I-130 RFE be rejected?

Check the rejection letter; it should have clearly stated the reason(s) better than this summary. Also, there might be some errors in the nature of the response to the RFE. Advisably, consult an attorney before you take further action.

It seems that the USCIS has made an inconsistent decision. On this basis, you should consult with an immigration attorney.

It is highly recommended that you consult an experienced immigration attorney to review your case and advise you why the petition may have been rejected and how to remedy your situation.

I would carefully read into their concern. If your divorce is not valid, then your marriage is not valid. Look at the issue raised and make sure you respond correctly. You may have to complete that divorce propriety and remarry, as it is likely USCIS will move to rescind the approvals if the divorce is not legal.

Check with the Reciprocity Schedule in the Foreign Affairs Manual for your country to see if the divorce was the correct one.

It is possible to receive an RFE on a particular issue that was not raised in a similar petition. Why? The answer simply is that a different CIS adjudicator my catch an issue or may raise an issue that did not seem to pertinent to a prior CIS adjudicator. As frustrating as this is, you have no alternative but to respond. Part of your response could point out that prior cases were adjudicated based upon the very same document that is being questioned with the RFE. But, in reality, you really have no alternative but to respond, if possible, with other proof of the divorce from your ex-wife or, as the case may be, that under the laws and practices within your home country the only evidence available is what you had previously submitted and which had previously been accepted in other cases.