I have an Endura and only recently I noticed it was becoming difficult to open. Upon close inspection it appears that the lock is rubbing against the bottom of the blade assembly resulting in metal shavings being left behind. These shavings are causing the action to feel gritty and stiff. I have cleaned out the action and lock as best as possible but have noticed that there is still friction occurring in the mechanism. I will put a drop of oil in the area when I get the chance. Is this wear and tear normal?