I just tried this in v18.104.22.168 on OEL5 and it works for me.
Check your keyboard shortcuts for Code Editor, Previous Word Start - confirm that it's set to Ctrl-Left.
My SQLDeveloper version is 22.214.171.124, OS: Windows XP.
Keyboard shortcuts are set properly.
In the example below I've used "|" character to show where cursor jumps after pressing Ctrl+ >.
"|pi|RBDKB|Tab|Knt |pi|RBDKB|Tab|Knt |pi|RBDKB|Tab|Knt|"
The pipe is being treated as a new word marker...but the feature is working.
select * from scott.emp - you can successfully navigate from word to word.
Check if the following preference changed / did not migrate between your 3.2 and 4.0 installs:
Tools > Preferences > Code Editor > Use Change of Case As Word Boundary
SQL Developer Team
This is it: Tools > Preferences > Code Editor > Use Change of Case As Word Boundary
Thanks a lot!