My opponent in a recent friendly match encountered this bug. Opponent attacked me with only Massacre Girl, Known Killer, which I believe was a 4/4 with wither due to its own static ability exactly as usual.
I controlled two white and blue 2/2 Knight creature tokens, created from Invasion of New Phyrexia. I used both tokens to block MGKK.
As combat damage was applied, 2 of the 4 from Massacre Girl KK was marked on each token. Due to wither this damage was dealt in the form of -1/-1 counters. Meanwhile, though, both tokens dealt damage as well, 2 each.
All three creatures died, which was correct.
However, I believe Arena then only caught one trigger of the final ability, and my opponent only drew one card. Both of my tokens had power and toughness 0/0. The triggered ability is not written “one or more” so it should have triggered twice and led to two drawn cards.
This bug was encountered as I used an iPad. Unfortunately I cannot provide a log because even though I used the client to try to make one, I am unable to find anything to share.