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I've been reading how to use the keyframer for motion, and it's working fine to move layers or custom brushes but everytime I use it, it seems to duplicate the source, and leaves the original drawing behind while the other one moves its position. How can I make sure there is no duplicated drawing left behind in the original position. If something pans offscreen, I don't want another copy left in the original position. What's the problem here?

Hi Mishiek, welcome to the TVPaint Community and Happy New year =)

If you define a source when you use the keyframer, you automatically "duplicate" your source. Because when you want to select a source, you mean "I don't want to apply my FX on the original source". If you want to move directly the original source, add the keyframer FX on the current layer, not on a new one and without selecting another source than "current".
If you prefer to select a source, you can hide the original layer (click on the green square on the timeline and make it red). You can also open a new project and select your source from the first project. Thanks to this, you're sure you won't have twice the same layer into the same project. =)