The woodruff key is what sets the sprockets timing and it should be a press fit holding it in place with the bolt torqued down. Looks to me that either the key was the wrong size or not seated when the sprocket was installed and torqued, keeping the sprocket from seating properly. I'd try the new OEM crank sprocket and woodruff key. I wouldn't file the crank or fill the sprocket with anything. Hopefully the sprocket seats on the crank like it should with the new key.

1990 LWB RS A/T
1990 LWB Base A/T
1991 LWB LS A/T Going...Going...