Steps to replicate the issue (include links if applicable):

• Open VisualEditor on a random page
• Add a link, either using the toolbar or using Ctrl-K
• Type in a valid character

What happens?:
The box does not give a dropdown list of suggestions consistently.

What should have happened instead?:

The box should always give a list of suggestions.

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):