I think the problem is that when the document view has focus, it is taking the mouse wheel scroll messages (which is why when we put the focus into a text box it works). I'll have a go at reproducing it here.
A more recent set of tutorials for 1.7 (and above) is available via affinity.serif.com or from Designer's Welcome screen.
The legacy tutorial set, also available on YouTube, includes:
1. Getting Started
• Discover Affinity Designer
• For Beginners
• For Beginners Too
• Using the Help System
• CMYK Setup
• Designing from a Sketch
• New from Clipboard
• Actual Size Zoom
• Editing PDF Text
• Using the Grade UI Kit
2. Artboards
• Artboards: Basics
• Artboards: Exporting and Printing
• Artboards: Colour and Opacity
• Artboards: From Content
• Artboards: Design Aids
3. Drawing Lines and Shapes
• Pen Power
• Shapes
• Convert to Curves
• Corner Tool
• Drawing Perfect Triangles
• Stylish Strokes: Textured Lines
• Stylish Strokes: Dashed Lines
4. Colour and Opacity
• Complex Gradients
• Adjusting Noise and Opacity in Fills
• Transparency Tool
• Changing Colours
• Blend Modes
• Colour Picker Tool
• Colour Palette from Document
• Colour Palette from Image
• Pantone Colours
• Global, Spot and Overprint Colours
• Quick Opacity Setting
5. Layer control
• Layers Panel
• Lock Children
6. Object control
• Selecting, Finding and Isolating Objects
• Rotation Point: Overview
• Rotation Point: Worked Example
• Vector Scaling Options
7. Symbols and Assets
• Symbols (1.5)
• Assets (1.5)
8. Painting
• Shading Using Raster Brushes
• Adding Raster Texture
9. Text
• Artistic, Frame and Shape Text
• Text on a Path: Overview
• Text on a Path: Worked Example
• OpenType Typography
10. Media
• Using Raster Images in a Composition
• Film Noir Style Illustration
11. Saving, exporting and sharing
• Save History
• Soft Proofing
• Exporting
• Exporting: Layers
• Exporting: Slices
• Exporting: Continuous
• Exporting: Automatic Directory/Folder Creation
• Exporting: Multiple Outputs from a Single Slice
• Exporting: Transparent and Coloured Backgrounds
• Exporting User Settings and Keyboard Shortcuts
12. Design Aids
• Constraints: Overview
• Constraints: Worked Example for Web Design
• Snapping and Dynamic Guides
• Snapping: Candidates
• Snapping: Object Creation
• Snapping: UI and Web Design
• View Modes and Split View
• New View
• View Points
• Grids: Icon Design
• Grids: Floor Plans
• Isometric Grid Drawings: Part 1 (Single Planes)
• Isometric Grid Drawings: Part 2 (Multiple Planes)
• Isometric Grid Drawings: Part 3 (Layers and Compounds)
• Grids: Coloured Lines
You can change the amount of decimal points you see by going to Affinity Designer > Preferences > User Interface here you will see the decimal point options for the different units of measurement within the program. You can set each unit up to a maximum of 6 decimal places :)
