A team has finished a game with 6-6-6 runs-hits-errors line 3 times since 1897, most recently New York Yankees on 15 May 1925. That is about one every 147,668 team-games.
Box score for the most recent one ↗
6-5-8 6-6-1 6-6-3 6-6-0 6-6-2 6-6-4 6-6-6 6-6-5 6-7-2 6-7-1 6-7-4 6-7-3 6-7-0
The whole distribution — Runs-Hits-Errors Lines · All 18 shapes