https://www.mlb.com/video/altuves-odd-ground-rule-double/c-2060415683?tid=63817564
That happened in today's Astro's-Indians game. Certainly not something you see every day. I didn't catch all of it, but I believe the explanation given on the telecast was that the ball was no longer "in flight" after it hit the fence. I'm a little surprised this is treated differently than a ball bouncing off the top of the wall given the rarity of this happening.