Got impossible damage rolls in a C&E tournament battle, played in Doubles OU.
Battle:
http://replay.pokemonshowdown.com/gen7doublesou-657738399
Luckily I used Knock Off with Pansage the first turn, so that it is clearly visible that the opposing Mantyke was itemless when the impossible rolls against Baltoy, which had a never consumed Wiki Berry, occured.
The first roll of 51% is possible assuming no SpA investment and a -SpA nature, which is very unlikely to be the case.
0- SpA Mantyke Scald vs. 252 HP / 4 SpD Baltoy: 138-164 (48.5 - 57.7%) -- 94.9% chance to 2HKO
The second roll, after Baltoy's Calm Mind, was too high, as the calc shows:
0- SpA Mantyke Scald vs. +1 252 HP / 4 SpD Baltoy: 92-110 (32.3 - 38.7%) -- 98.3% chance to 3HKO
Also, the "Ready" button did not work when I tried to accept my opponent's challenge in the AAA tournament in the OM room. Cleared Cookies and Cache and tried it on my phone without success, so it is clearly an issue of Showdown and not a local one.
Edit: asked my opponent about the Mantyke's spread - it was max SpA and SpDef. And here are the calcs, how much damage it should have done:
252+ SpA Mantyke Scald vs. 252 HP / 4 SpD Baltoy: 236-278 (83 - 97.8%) -- guaranteed 2HKO
252+ SpA Mantyke Scald vs. +1 252 HP / 4 SpD Baltoy: 156-186 (54.9 - 65.4%) -- guaranteed 2HKO
This means the rolls inbattle actually were far too low.