Why are people playing my mission getting errors for addons that I previously removed from the mission?

If you designed a mission that previously used addons and later deleted those addons from the mission using the Mission Editor, other people who try playing the mission may still get error messages that the addon is required.

This is because previous references to the addon in one of the MISSION.SQM file's ADDONS or ADDONSAUTO sections are not deleted by OFP's Mission Editor when you delete all of the addon's units from a map.

You'll have to edit the MISSION.SQM file with a text editor and manually remove all references to the specific addon.