Are you on a Mac? If so, preferences is under the SQL Developer menu, not Tools.
Try Tools > Features > Clear Cache to see if that does anything to help, or even delete system_cache, system_cache_1, etc., folders under your user settings for 4.1.5 (C:\Users\<your_userid>\AppData\Roaming\SQL Developer\184.108.40.206.78). Close SQL Developer first and re-open after doing the delete.
Otherwise, I would try nuking the user settings for 4.1.5 entirely, then re-open SQL Developer (skipping the migrate user settings step).