El-table 合并部分成功部分失败，如何解决？

<el-table :data="waterData" border :span-method="handleSpanM">
  ...
</el-table>

export default {
  methods: {
    handleSpanM({ row, column, rowIndex, columnIndex }) {
      if (columnIndex === 0) {
        return { rowspan: row.length }
      }
    },
  },
};

export default {
  methods: {
    handleSpanM({ row, column, rowIndex, columnIndex }) {
      if (columnIndex === 0) {
        // 获取当前行与下一行name相同的行数
        let count = 1;
        for (let i = rowIndex + 1; i < row.length; i++) {
          if (row[i].name === row[rowIndex].name) {
            count++;
          } else {
            break;
          }
        }
        return { rowspan: count }
      }
    },
  },
};

<el-table-column width="65" disabled>...</el-table-column>
<el-table-column width="70" disabled>...</el-table-column>
<el-table-column width="120" disabled>...</el-table-column>
<el-table-column width="180" disabled>...</el-table-column>

<el-input disabled size="small" v-model="waterForm[`water${index + 1}_label`]" ></el-input>