ALT_CLOSE and defaultPricingField is null

We use a service to pull historical data and would like to get clarification regarding the pricing fields.

The service we use is:

https://api.refinitiv.com/data/historical-pricing/v1/views/interday-summaries/{symbol}

We typically retrieve the fields: "TRDPRC_1", "OFF_CLOSE" for closing price and determine the appropriate closing price based on the "defaultPricingField" and "ACVOL_UNS" for volume in units.

However, we’ve noticed that for certain RICs, even on trading days with a volume greater than 0, both "ACVOL_UNS" and the value returned by "defaultPricingField" (TRDPRC_1/OFF_CLOSE) are null. Instead, a new field, "ALT_CLOSE", is returned and appears to represent the correct closing price for that date.

This behavior occurred with the RIC WWT.V on the date 23.05.2025

Request:

https://api.refinitiv.com/data/historical-pricing/v1/views/interday-summaries/WWT.V?start=2025-05-23&end=2025-05-23

response (full response attached):

"data": [

            [

                "2025-05-23",

                null,

                null,

                null,

                403,

                null,

                null,

                0.005,

                0.005,

                null,

                null,

                1,

                1,

                null,

                2.015,

                0.005

            ]

        ]

Could you please clarify the meaning and usage of the "ALT_CLOSE" field, and under what conditions it is returned instead of the usual fields?

Thank you in advance for your help.

Best regards,