I just posted about vector brush pressure problems in the Affinity Designer for macOS thread, but here are the problems I'm experiencing with the iPad version.
The strokes are not responding to pressure applied with the Apple Pencil while creating the stroke, but they do respond to edits made to the pressure curve. However, the nodes on the pressure curve in the panel snap back to the top after adjusting them, even though the stroke shows variable pressure is applied, and the overall stroke width slider produces no effect. Once I tap the move tool the pressure curve displays normally again, and the stroke width slider behaves normally.
I had used the app for several hours today before these problems presented themselves. Strokes responded to pressure applied by the Apple Pencil when drawn, and each drawn stroke was able to be fine-tuned by editing the pressure curve without manually switching to the move tool after each stroke.
brush-pressure-ipad.MP4