I think I found an error in Affinity Photo. I use Affinity Photo in the latest version (126.96.36.1992) with Windows 11 in the latest version (21H2, Build 22000.556). In the Affinity programs, you can quickly and easily set the brush width and hardness by pressing Ctrl + Alt (on Windows) and moving the mouse up, down, right or left. There is also the possibility to rotate the entire document by pressing the alt key and rotating the mouse wheel. If you press the Ctrl key, the whole document rotates in (I think 15°) steps.
If you now set the brush size or hardness in this way, then rotate the document and then want to change the brush size or hardness again, the directions in which you have to move the mouse to the adjusting size/hardness are constantly reversed. It also happens that both values are adjusted at the same time if you move the mouse only in one direction. Between rotating the document and adjusting the brush, I always released the Ctrl and Alt keys. But it also happens if you press them continuously.
By the way, the error occurs not only in Photo, but also in Designer and Publisher with all kinds of brushes (including erasers, selection or restoration). The error is reproducible and also occurs in new documents. However, the document is not completely empty, but must contain at least one object. I only noticed the error since the update to 1.10.5. But I'm not sure about that. The error only occurs when rotating the document in increments using Ctrl + Alt + mouse wheel. I think there is a conflict with the keyboard shortcuts. If you want to reproduce the error, follow the instructions:
Create a new document in Affinity (Photo, Publisher, Designer).
Paint something in the document with a brush.
Press Ctrl + alt and move the mouse up, down, right or left to change the brush in size and hardness.
Press Ctrl + alt and rotate the mouse wheel to rotate the document to the right or left and paint something again.
Adjust the brush size again (release the Ctrl and Alt keys in between or press continuously, bolth works). Now, the error will occur. If not, turn the document another 2-3 times and change the brush settings and paint something. In the
attached video, the error can also be seen again.