Getting Issues In Unified UI in Case Entity

Hello Experts,

I got the opportunity to work on Unified UI Version :9.0.1.731 (DB 9.0.1.731).
I am having a business rule on a Case Entity.

The business rule as follows: 
Making a Description field optional/required based on the Contact Lookup field.

The business rule is hitting. But getting following issue in description field.This is happening in Unified UI.

 There is no Js, No plugin .Nothing except one business rule.Is it a product issue?

Thanks,
Jagannath