Problem show themselves as:

1. 'view inheritance' - newly opened images inherit the position in the image area being shown and the postion of scrollbars fron the previously opened image, this result in glitches as unnecessary scrollbars in small images which fit the program window's size, or unnecessary scrollbars+new image scrolled out of the program's window;
2. 'missing scrollbars' in large images (perhaps it's another instance of 'view inheritance', when a larger image is opened after a smaller image) - an image which exceeds the size of the program window is initially displayed without scrollbars; the appear only upon resizing the program window, scrolling the image with the mouse wheel or repainting the window when it gets covered by anothe one;
3. "file .. cannot be loaded' message - if you opened an image with 'missing toolbars' effect and resized the window, scrolled the image so that the toolbars appeared, and then you try to open another larger image, you may get a message "file ... cannot be loaded", this happens with some images, it seems that with large ones, like 7600x6500px.
   They seem interrelated, seems like some inconsistences in the messaging mechanism or GUI behaviour between Win and ROS and not mspaint itself.
   VIEWS OF THE GLITCHES:

MS Paint in Win11 supports Layers, I wonder if ROS Paint will add layers (for providing a better Paint for ROS/older windows)?

and there is some more features in post-XP/Vista Paint that may worth providing in ROS Paint:

• Shapes
• Brushes
• Crop canvas to selection size

Drawing in XP MSPaint feels snappier. This is made evident when zooming in and rubbing pencil tool with speed, across canvas.
Two things are seen:

• a perceptible lag between drawing and mouse cursor, as RPaint waits for latest point to complete a line segment.
• coarser lines with fewer segments in RPaint compared to MSPaint.

Methinks that MSPaint samples mouse more often.

Original MSPaint has some nifty and not so obvious behaviours. Maybe they can make their way into RPaint(as-is or refined).

• the zoom has a 10x level. You have to click pixel perfect at bottom of zoom selector. Or can cheat and lengthen the zoom selector to have more area to click(windowspy or hexedit exe).

• Shift + (L or R)Click + Drag has meanings depending on context.

  • With a pencil/brush, it locks drawing in straight line(hor, vert, diag).
  • With line, it does same locking, except you can rotate it in 45deg angles.
  • With selection, it stamps that selection down like a brush.
  • Eraser R click(colour mask eraser) already implemented.

• Ctrl + NumPlus/NumMinus changes the size of brush, including those that don't have size option.

  • Makes pencil/brush nib smaller or bigger.
  • Resizes selection by 2x or 0.5x.
  • Plays poorly with undo.

• There's probably more, but I forgets.