The text objects and the grease pencil drawings lie in the same plane. Visibility is therefore depending on the drawing order, also Z-fighting may occur. I would suggest to move the text slightly along the Y-axis in order to position it in front of the grease pencil drawing. Another approach is to change the Stroke Depth Order for the grease pencil objects from 2D Layers to 3D Location. This seems to work as well, although Z-fighting may still occur.