Hi iabhisheksinha
As per my observation, when you write the display date pattern make sure you are entering the date same as the provided format i.e. MM/DD/YYYY [including '/' as well] in your case. If you enter 12042019 instead of 12/04/2019 [As mentioned in above pattern] then it will be counted as invalid.
Also, if you want to make 12042019 format working, then you have to provide pattern in the format i.e MMDDYYYY or for an alternative you can add custom java script code that will convert the entered number in the date pattern format and output the result.
Hope it helps!