2nd gear downshift grind

Besides what has already been mentioned, possibly poorly adjusted or worn clutch and/or shift linkage; insufficient clutch plate departure;
What you can TRY to do for the meantime is matching rpm's on down shifting. After some trial and error, you'll find the rpm sweetspot you need to match by blipping the accelerator for downshifting more smoothly. When I had a a 60's foreign sportscar I learned to do that.