云数据事务报错:ResourceUnavailable.TransactionConflict?

"document.update:fail [ResourceUnavailable.TransactionConflict] Transaction is conflict, maybe resource operated by others. Please check your request, but if the problem persists, contact us.; at document.update api; "

云数据库的一个简单事务处理，代码如下：

    const cmd = db.command;

    const updtranscation = await db.startTransaction();

    res = await updtranscation.collection('xinfo').doc(_id).update({

      data: info

    });

    if(info.total_pay>0){

      res = await updtranscation.collection("xaction").doc(info._id).update({

        data:{

          total_pay:cmd.inc(info.total_pay)

        }

      });

    }

    updtranscation.commit();