Custom Span Tags Cause all Heading on Page to Change

Issue Summary

When creating a page and formatting specific sections that have a <span> tag seems to cause unwanted effects when trying to switch a single heading, which causes the whole page to also get changed to the same formatting. This can be a major pain point if users copy over information that introduces these span tags into their connect.

Steps to Reproduce

1. Edit a page with several different headings already on there (H1, H3, Pre-formatted).
2. Introduce a <span> tag to modify anything within the line.
3. Simply put the cursor in middle on line on one of the headings
4. Change the heading to another heading, such as H3 to Pre-formatted

Expected Results

Only a single line should change.

Actual Results

The whole page is changing to the same formatting.

Workaround

Currently, the workaround is to remove the <span> tags.