This behavior can happen under a few different scenarios. 

First, eliminate a caching behavior. Here is a 3rd party link on how to clear cache. Note: We provide links to third-party websites in an effort to help you resolve your issue. We are not responsible for the information on third-party websites and we cannot assist with implementing resolutions from these websites.

If the behavior persists after clearing your cache, this may indicate there is an errant character somewhere in your part's content. This errant character would be, for example, an ASCII character. You may not see the ASCII character off first glance, but to help in locating it you may do the following:
  1. Copy the Source Code of the part from the content from under View>Source Code
    • Note: This is assuming that you're using a part that has Source Code
  2. Paste the Source Code into a text editor, like Notepad
  3. Save the Source Code to a local location, as a backup
  4. Review the Source Code in notepad and check for anything that looks awry
  5. Remove the ASCII character from the Source Code
  6. Copy the Source Code
  7. Paste back into the Source Code area in the part
  8. Click Save