Sometimes I observe that when users click on the submit button the collection is not populating with the data which is selected/entered by the user in custom input or dropdown.
And one another thing is some users pass the blank value in the input via spacebar & after that will able to submit the custom form.
I just tried to reproduce this but was not able to at all. Are you able to make a short screen recording showing this data not being captured?
In regards to the space character being used to get passed an empty state, there is a feature request that will take care of that one: Data Validation | Voters | Adalo