This happened pretty fast because it’s right in the middle of battle phase so I would like others to confirm if they also observed this bug.
Somberwald Alpha’s is very similar to Embermaw Hellion’s bug not resolving properly upon death. The text of Somberwald Alpha says “When creatures you control are blocked, the blocked creature gains +1/+1 and Trample until the end on your turn.”
So I have 2 creatures and opponent has 2. My Somberwald Alpha attacks the opponent’s blocker, triggered the +1/+1 and trample. Both my Somberwald and defender dies. My second creature attacks my opponent’s second creature (which has vigilance). But my second creature did not get the +1/+1 and trample buff from Somberwald Alpha because it Somberwald already died.
Creature deaths should be resolved all at once to ensure that these abilities stay active during the entire combat phase.