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Since I kind of gave you partial info, and wanted to see what I was missing myself , I made a simple rotating box so I could see what needed to be done.
It does need the tick18_ name so call it tick18_door or something like that.
With the animated part selected go to fstools and open the animation manager. In the upper right corner you should the name of your part.
Under “groups” you should be on “all” – under “animation list” select Ambient. On the right you see “object anims”, below that is a start and end box. Click create. In “start” put in where your animation starts (usually 0 ) and where it ends . If your animation goes to 100, put in 100 for end. Now click “update sel” at the top.
You should be ready to export, make sure you click “export animations”