Correct links to menu items in Joomla
The issue is that menu item link can be also changed, i.e. from /forum to /forums (if menu item alias was changed) or from /forum to /joomla/forum (if site was moved to /joomla subfolder or menu item was moved to new parent) or from /index.php/forum to /forum if 'Use URL Rewriting' setting is enabled.
There is a simple solution: don't use aliases in link URL but use raw link with menu item ID: index.php?Itemid=XX where XX is ID of menu item.
Joomla plugin 'System - SEF' will auto-convert such links to correct URLs which will reflect current menu item alias and current site location, so you can safely change menu item alias, move item to new parent or move site to any location.