While scrolling issue on Issue view screen, does not freeze the Summary panel at the top

Summary

When scrolling through an issue, the Summary top panel does not freeze on the screen. It scrolls with the screen.

Environment

1. In JIRA 7.1.10 (as well as 6.4.11), it was possible to freeze the Summary at the top of the screen.
2. In JIRA 7.3, the Summary field is scrolling with the screen. It does not stay on the screen.

Steps to Reproduce

1. Navigate to an issue on the browser on JIRA 7.3. Its better if the issue has a few comments so you can scroll on the page. (Tested on this site)
2. Scroll through the issue
3. The Summary field does not stay on the screen

Expected Results

The Summary field should stay on the screen just like earlier versions.

Actual Results

The Summary field does not stay on the screen.