Fields can't be updated on button click in stateless forms

Fields can't be updated on button click in stateless forms

There was a recent change in stateless form behavior and it requires an urgent fix.
When a stateless form button is clicked it no more executes the script which updates other fields from the form. 
It previously worked, now the same script no more works -  I guess that this is a problem related to the new UI. 
Please fix this as soon as possible. it currently breaks existing functionality in some of my applications (and I suppose that I am not the only one affected). 
I hope that this is not an intended (and not announced) change in stateless forms  behavior .  

Regards,
George