One potential solution to this problem is to try resetting the Dock. You can do this by navigating to the following directory in Finder:
~/Library/Preferences/
Once there, locate the file named "com.apple.dock.plist" and move it to the Trash. Then, restart your Mac. This action will reset the Dock to its default settings, which may resolve the issue with missing alias icons.
If resetting the Dock doesn't resolve the issue, you can try removing and re-adding the "Start" folder to the Dock. To do this, simply drag the folder out of the Dock until you see the "Remove from Dock" option, then release the mouse button. Next, navigate to the folder in Finder and drag it back to the Dock to re-add it.
Alternatively, you can try recreating the aliases within the "Start" folder. Sometimes, recreating the aliases can help refresh the icon display in the Dock.
If none of these solutions work, it may be worth reaching out to Official Apple Support for further assistance. They can provide personalized support and may be able to offer additional troubleshooting steps or insights specific to your situation.