This issue does not happen in a guest log in, it does on my main log in, OSX 10.13.6 Affinity Photo 1.8.3.
Do not remember any program crash or computer crash.
Used clean my mac to uninstall then reinstall Affinity Photo - did not resolve issue - must be some hidden preference or plist file.
Can you tell me where all plist - preference files are so I can delete then and reinstall Affinity Photo as totally clean install.
Was purchased through the mac app store (maybe that is an uninstall issue).
Issue
New File - New fill layer - Pen tool - draw selection/close selection - press Selection, the selection and curve disappear, it looks like multiple actions are happening, it looks like it makes the selection mask but then it disappears. Are there actions in Affinity Photo?
Anyways this does not happen in a guest log in - so I can continue to work.