Link Checker stops running shortly after server restart

The Link Checker does not run consistently - the service seems to "stop." Each time we restart the server, it runs for a little while, and then stops again. It does not finish "crawling" the spaces. It does not find all known broken links, and the date in the "last checked" column does not change. The queue size (Main.CheckLink) also "freezes" after a certain point.

• Xwiki.properties is configured with "rendering.transformations = macro, linkchecker".
• We visit all the links (some pages have known broken links, and we watch for those).

Help is greatly appreciated as we really would like to use XWIKI as our primary wiki tool, but the ability to managing broken links is a priority business requirement at our company. I am submitting this JIRA as requested on the discussion forum at http://xwiki.475771.n2.nabble.com/Question-About-Link-Checker-Module-tp7580939p7583207.html.