Pull Request description is not updated when target branch is changed

In a created pull request, the description field is often not being filled with the list of commit messages. When changing source/target branch as well, the description field is not updated with the list of applicable commits.

This issue was tested on the following browsers.

Does not work

1. Google Chrome
2. Mozilla Firefox

Works

1. Microsoft Edge

In the image below, it shows that Source Branch B1 to be merged to target Branch master. The PR description didn't change as the PR is showing the description when the source branch was B2.