Communication tab not working for custom entities in Sage CRM 2019 R1

I am trying to create custom entity (say Contract) in Sage CRM 2019 R1 with Advanced Customization wizard.

While creating Entity with Advanced Customization wizard, we have selected Owned By Opportunities, Has Communications and Has Library options only.

After that when we access any Opportunity record and we are able to create Contract record successfully. But when we try to create communication for that particular opportunity then

1. Communication New Screen is properly visible.

2. when i click on Cancel button, it navigates to some other screen,

3. When I enter all details of communication and click on Save button, it doesn't navigate to the Communications tab of Contract entity.

4. When we keep one of the mandatory field as blank and hit save button, it doesn't navigate to the Communications tab of Contract entity.

Having hard time to understand root cause of this behavior as entity is created by Advanced Customization wizard.

Let me know if this is known issue with Sage CRM 2019 R1. if this is known issue, then do we have hotfix for this.

I tried to replicate same thing in Sage CRm 2018 R3 and found same results.

Not sure what I am missing here.

Any help will be appreciated.

.