Hello @pench!
I found another post in our forum about validating forms inside of stepped containers. It looks like there is a solution marked where the user combined some steps from previous commenters along to get the intended validation logic.
Hopefully that helps to solve the issue for you!
That is odd behavior that the validation only kicks in once data has been entered in and then deleted. I will look to reproduce this and file a bug report for you once I can confirm the steps for reproduction.
It looks like you removed the form's default submit button, is that correct? So that the 'Next' button has event logic for submitting the form and moving to the next step, correct?