Hexarachet swivel block

I recently purchased a used flying scot and have a wonderful summer of sailing. What a great boat. One problem, when tacking my mainsheets get caught in the swivel assembly because it does not swivel 360 (it is stopped by screws on either side half way). As a result when the main is pulled in tight there is no where for the sheets to go when tacking and they get caught behind the lifting strap assembly. Is it supposed to swivel 360 ? Maybe I need to back the two secrews out.
Thanks, Beth