I Noticed today, that when I try to delete vector layer, the bitmap drawing is strangly moved bottom left, and reduced.
From a new project (from scratch), this can be viewed by, just after removing the vector layer, drawing at upper left top. the drawing will appear at bottom right.
Another problem. When draws are done on several bitmap layers, during play, the layer below the current selected one display only keyframes at keyframe time and no frame between them.