How to create a summary table for Sankey chart?

I possess data similar to the images shown. I aim to develop a Sankey chart that incorporates date and product ID filters. The data involves a many-to-one relationship connecting 'Redeem_start,' 'Redeem_fail_type_1,' 'Redeem_fail_type_2,' and 'success_redeem' with 'users' and 'calendar,' linked through 'user_id' and 'date.' I've compiled a summary table, but it isn't functioning as anticipated, as it erroneously includes data from Stage 2 in the calculations for Stage 1.
Sankey_Data =
UNION(
    SELECTCOLUMNS(
        Reward_Started_Summary,
        "User ID", 'Reward_Started_Summary'[user_id],
        "Product ID", 'Reward_Started_Summary'[product_id],
        "Date", 'Reward_Started_Summary'[Date],
        "Stage 1", "Reward Started",
        "Stage 2", "Reward Started",
        "Reason", BLANK(), // Since there's no reason in the start stage
        "Count", 'Reward_Started_Summary'[Count]
    ),
    SELECTCOLUMNS(
        Failed_Reward_Summary,
        "User ID", 'Failed_Reward_Summary'[user_id],
        "Product ID", 'Failed_Reward_Summary'[product_id],
        "Date", 'Failed_Reward_Summary'[Date],
"Stage 1", BLANK(),
        "Stage 2", "Reward Failed",
        "Reason", 'Failed_Reward_Summary'[reason],
        "Count", 'Failed_Reward_Summary'[Count]
    ),
    SELECTCOLUMNS(
        Catalog_Redeem_Summary,
        "User ID", 'Success Redeem'[user_id],
          "Product ID", 'Success Redeem'[product_id],
        "Date", 'Success Redeem_Summary'[Date],
     "Stage 1", "Reward Started",
        "Stage 2", "Success Redeem",
        "Reason", "Success Redeem",
        "Count", 'Catalog_Redeem_Summary'[Count]
    )
)