I have the exact same problem. When i shift into 6th gear for the 1st time since starting the engine, it grinds pretty loud,(clutched all in) but when I downshift to 5th gear, and go back to 6th after awhile, no grind. Also the first time I put it in 6th, it feels a lot harder then the 2nd/3/4/5th time.

Help :{