When rotating the view the ruler indicators start going their own way. For example, when moving the mouse to the top-right corner, they seem to follow the coordinates as if the canvas was still normal. However, after rotating multiple times they completely lose their marbles. At 45° the top ruler is stuck in the center and 90° is my favorite when they move in the opposite direction of the mouse.
See video (6.3 MB)
Steps to reproduce:
View menu > Rotate Right
Move mouse over canvas and watch the rulers
View menu > Reset Rotation to recover
Affinity Designer v1.6.0