DMS| Preprod | Mandatory Validation is not working on preview form page

Steps:

Create PDF template
Navigate to Send Form
Select any Template
Provide Email id and subject
Click on Preview Form
Remove Date of joining from the field (if present)
Click on Send
An error is displaying

Now provide Date of joining, user will be able to send form,

Expected: A validation message should be display as Date of Joining is mandatory field