0 (zero) is not a valid 1099-R box 12 entry. Box 12 must either be BLANK (and if it is then boxes 13 & 14 must also be BLANK), or it must have a positive dollar amount. (A zero in box 12 says that state tax was withheld but it was zero which is contradictory.)
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**