New to Affinity Photo and a Photoshop convert. Glad I found this topic because I experienced a similar thing.
I use a MacBook Pro for editing. With Photoshop I got into the practice with pinching the trackpad to change zoom levels. And if not careful with the movement of your pinch with AP you can accidentally rotate the image instead of zooming (with PS it took a defined and purposeful motion to rotate instead of zoom so couldn't accidentally be done). And when the image rotates,,, the Rulers display changes to this weird decimal number that is no longer coordinated with the image. Even when the image is rotated back,,, the Rulers change persists and the only way to reset them is to close and save the image then reopen it.
Is this a bug in the program? Is there a way to reset the Rulers once this happens other then closing the image then reopening it?