This is with Affinity Designer 2.2.1.2075 on Windows 10.
It seems to happen with Layers specifically. Triggering creation within the root Artboard doesn't cause the same garbled screen updating behavior when a Pixel Layer is created using Assistant.
Steps:
1. Start document with Artboard
2. Switch to Pixel Persona
3. Create a Layer
4. Start drawing inside Layer forcing creation of a Pixel Layer using Assistant.
5. Reap:
23.10.22_11-36-18-AM_NV12_1920x1080.mp4
test-document.afdesign