Missing Tags

Strange one here guys and gals.
The steps to create this issue is to create a post, add some tags. publish post.
here is where it’s getting strange I have a number of posts all with tags. but when in the front end of the site, only some of the tags are being displayed in the tag cloud, and when I click on any of the tags in the tag cloud they don’t complete i.e. you end up on the tag search results page saying “nothing found”.

Then when in the admin area, the tags are intermittently being displayed and not displayed, in the list of posts… very strange. Anyone run across this issue?

Thanks in advance for any help.