Didn't work, but good guess! However, I tried setting the sprite to use another image (renderImgX) just before rendering to the real image (renderImg). Works!
setSpriteImage(renderSpr, renderImgX) rem AGKs fix
Update(0) //update sprite positions
SetRenderToImage( renderImg, 0) //set the world to render to the Texture Image
ClearScreen() // Clears back buffer and fills it with the chosen clear color
//Render2DFront() //render the world to the Texture Image ...
Render()
setSpriteImage(renderSpr, renderImg) rem AGKs fix