Found a way to fix the bug in the case : kerbal died, been restored. It's hacky, but it fixes the bug. So go to newly made quicksave.file (game location/saves/campaign-name) from there open the new save file in notepad, txt, enable edit on the file, find the kerbal/s under ROSTER, which are making you the trouble, find their flight log and delete the line of the log that mentions n(number) - Die, remove them all from the log of the kerbal. After saving, you can load up the save and they will gain the xp that's missing. You can do it while the game is running.
Hopefully that helps a lot of lazy people that do not want to fly their kerbals around to gain xp.
