回复：问什么母亲的130批准后又被重新review？

母亲的130一个月前批了，收到了批准的信。可刚又接到USCIS的信，说case被Department of State退回了，要按Department of State的要求重新处理，信里没说退回的原因。
-After USCIS approved the I-130, they sent it to the National Visa Center (NVC) of the Dept of State. Thne, NVC will contact you and send you the instructions. Something may be wrong in the I-130 and NVC sent it back to USCIS. Are you sure you selected the Consular Processing in the I-130 so that you mother can get the immigratuion visa in China? I suggest you to contact USCIS by calling or visiting the local office to see what happened. Normally USCIS will not deny the approved I-130, and they may just fix it and send it back to NVC again.

有没有人有这方面的经验，一般是什么原因批准的case会被Department of State退回？这个重新处理会多长时间？有什么办法知道退回的原因？有什么办法加速这个处理过程？

母亲的基本情况：
7年前来过美国一次，待了一年，有延期证明，按时回国。但后来连着三次visa申请都被拒了，主要原因是孩子都在美国，老太太就再也不去申请visa了。这次好说歹说同意办绿卡再来美国玩一段时间。


提前谢了。