o2deprived

Hi dorian_grey,
Your observation is correct. Both the X/Y coordinates of the artboards and their dimensions are not pixel integer values which leads to the variation you are seeing when exporting the files.
To prevent this from happening make sure you have Force Pixel Alignment in the Snapping Manager (menu View ▸ Snapping Manager...) enabled from the beginning. If you enable it now you will still have to adjust the X/Y coordinates and artboards dimensions manually if they are not integer values otherwise moving the artboards a little should align them automatically with the pixel grid.

Hi  Checkmate,
Check the X,Y coordinates of the artboard(s) in the Transform panel (make sure their layer is selected in the Layers panel). Are they integer values? You may have to increase the number of decimal cases displayed in the X,Y fields in the Transform Panel going to Affinity Designer Preferences ▸ User Interface section and increasing the value in the Pixel field in the Decimal Places for Units Types section. If setting them all to integer values doesn't fix the issue can you please attach the afdesign file here so i can take a look please? I can provide you with an upload link if you prefer to keep it private.