If you're hearing sibilance well then by golly you're hearing it! It's there for some reason and anyone who cares about this would have, should have, offered to help, not ridicule.
Why there wasn't more interest in helping you solve it is beyond me. It is possible that that particular piece of vinyl wasn't quite ready for pressing, and for some reason the attacks on vocals are "vomiting" your cartridge as it hits those transients. If this doesn't happen with any other recordings, so please be honest here, then it is not your cartridge or table. Remember, mono recordings modulate only in the horizontal, there is no vertical motion of the stylus. Make sure you run at maximum VTF as recommended by the cartridge manufacturer when playing mono records.
Why there wasn't more interest in helping you solve it is beyond me. It is possible that that particular piece of vinyl wasn't quite ready for pressing, and for some reason the attacks on vocals are "vomiting" your cartridge as it hits those transients. If this doesn't happen with any other recordings, so please be honest here, then it is not your cartridge or table. Remember, mono recordings modulate only in the horizontal, there is no vertical motion of the stylus. Make sure you run at maximum VTF as recommended by the cartridge manufacturer when playing mono records.