Solução: eu desinstalei completamente o software de tablet da Wacom 6.3.16-12 e mudei novamente para 6.3.15 -3. Além disso, certifique-se de remover todos os arquivos de preferências, incluindo as seguintes sobras:
/Volumes/MacBook/Library/Internet/Plug-Ins/WacomTabletPlugin.plugin
/Volumes/MacBook/Library/PreferencePanes/WacomTablet.prefpane
/Volumes/MacBook/Library/Frameworks/WacomMultiTouch.framework
/Volumes/MacBook/System/Library/Extensions/Wacom/Tablet.kext
/Volumes/MacBook/Library/Receipts/Wacom/Tablet/Docs.txt
/Volumes/MacBook/Users/yourusername/Desktop/Preferences.wacomprefs
/Volumes/MacBook/Users/yourusername/Library/Preferences/com.wacom.wacomtouch.prefs
/Volumes/MacBook/Users/yourusername/Library/Preferences/com.wacom.wacomtablet.prefs
/Volumes/MacBook/Library/LaunchAgents/com.wacom.wacomtablet.plist
/Volumes/MacBook/private/var/db/receipts/com.wacom.TabletInstaller.plist
/Volumes/MacBook/private/var/db/receipts/com.wacom.TabletInstaller.bom
/Volumes/MacBook/Users/yourusername/Library/Application/Support/com.apple.sharedfilelist/com.apple.LSSharedFileList.ApplicationRecentDocuments/com.wacom.removewacomtablet.sfl
/Volumes/MacBook/Users/yourusername/Library/Saved/Application/State/com.wacom.RemoveWacomTablet.savedState
/Volumes/MacBook/Users/yourusername/Library/Preferences/com.wacom.RemoveWacomTablet.plist
Eu passei horas na depuração. Esse problema está definitivamente relacionado à atualização do software da Mesa Gráfica Wacom 6.3.16-12. Além disso, está relacionado a falhas aleatórias no sistema e mensagens de erro infinitas no log do sistema operacional do OS X.