salweek pre is running long, query on daily_data is slow

salweek pre runs much quicker the first weekend after month end close. From the next weekend onwards its run time keeps increasing week after a week till the next month end. We are on version 13.1. Does anyone has ever come across this issue?

Below is the explain plan:

Plan hash value: 2834824607

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| Id  | Operation                           | Name          | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     | Pstart| Pstop |

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|   0 | SELECT STATEMENT                    |               |  9011K|   369M|       |    41M (42)| 00:03:29 |       |       |

|   1 |  HASH GROUP BY                      |               |  9011K|   369M|   586M|    41M (42)| 00:03:29 |       |       |

|   2 |   PARTITION RANGE ITERATOR          |               |  9011K|   369M|       |    24M (61)| 00:02:05 |   179 |   180 |

|   3 |    TABLE ACCESS BY LOCAL INDEX ROWID| DAILY_DATA    |  9011K|   369M|       |    24M (61)| 00:02:05 |   179 |   180 |

|*  4 |     INDEX SKIP SCAN                 | PK_DAILY_DATA |   121K|       |       |    12M (60)| 00:01:02 |   179 |   180 |