Unfortunately, unrealBook has a bug where non-pro iPads do not draw correctly if Apple Pencil is enabled. This will be fixed on 4.1.2. So for now, please do the following. Turn off Apple Pencil drawing and clear the drawings for the file that didn’t draw properly.
Turn off Apple Pencil Drawing – Settings->Global->Functions
Then clear the drawings from the files that didn’t draw properly. Settings->File
This will fix the problems until version 4.1.2 is released.