UNEXP_ERROR : ORA-00001: unique constraint (INV.MTL_ITEM_REVISIONS_B_U3) violated in Package INV_ITE

Hi, I'm getting the following error:UNEXP_ERROR : ORA-00001: unique constraint (INV.MTL_ITEM_REVISIONS_B_U3) violated in Package INV_ITEM_REVISION_PUB Procedure Create_Item_Revision

when trying to run INV_ITEM_REVISION_PUB.Create_Item_Revision API in a cursor loop.  Error is always on the 2nd call to it, so I'm sure there is a REVISION_ID sequence which is not getting it's .nextval applied

I tried all possible true/false combinations of p_init_msg_list and p_commit.   e.g.
              p_init_msg_list => FND_API.g_TRUE,
              p_commit => FND_API.g_TRUE,