Steps to reproduce:

Create a page in Confluence with the following contents:

1. Line 1:

   <ac:structured-macro ac:name="code">  <ac:plain-text-body><![CDATA[this is my code]]></ac:plain-text-body></ac:structured-macro>
   

2. Line 2:

   <ac:structured-macro ac:name="code">  <ac:plain-text-body><![CDATA[this is my code]]></ac:plain-text-body></ac:structured-macro>
   

   Test for Line2

3. Line 3:

   <ac:structured-macro ac:name="code">  <ac:plain-text-body><![CDATA[this is my code]]></ac:plain-text-body></ac:structured-macro>
   

   Place the cursor at the end of the "test for Line2" and press enter and then save the page.

Actual behavior:

When you save the page, the enter after the "Test for Line2" doesn't show.

Expected behavior:

Confluence should respect the changes and show the enter.

Workaround:

Type a dummy word or blank space after pressing enter and then save the page and edit again and remove it.