Select control value property in repeat doesn't work

I have a select control in a repeat with this expression:
dmx-on:changed="dd_products.select(value);inp_UnitPrice1.setValue(dd_products.data.UnitPrice)"

And it doesn’t work. If I change ‘value’ inside the parenthesis to a hard-code value (i.e 10 or 14, etc) it works for that value.

This works:
dmx-on:changed="dd_products.select(10);inp_UnitPrice1.setValue(dd_products.data.UnitPrice)"
Any ideas why this isn’t working or what the correct expression should be?