Calculations not working on programatically added repeater rows

Just started with this plugin, and really impressed -nice work!

I am seeing something strange though..

I have a repeater row with a calculated value (rate * qty), which works beautifully through the front end ACF Form or Admin page.

But when I add a repeater row through a function, the total value is Zero.

Manually entering each post and Updating it (even without changing any values) fixes the value.

Any thoughts, please?
Best Regards (And Seasons Greetings),
Dave