I have been having this issue for some time, and it's suuuuper frustrating to the point where I am considering other options regretfully as I really love affinity photo.
1. I was working in affinity, mainly using the brush tool doing some tracing.
2. I CTRL+V an image onto the canvas as seen in the screenshot
3. Tried to zoom in using the space + control function and would not zoom in or out properly
4. I then tried selecting the brush tool and for some weird reason, only drew straight lines ?!
This has happened to me at least 5+ times in the last weeks or so, is it a bug ? a known issue ? is there a fix ? I really look forward to your help.