Yet another It That Rides bug

Delnai

I had an 8/8 It That Rides as One (stolen from my opponent, in case that is relevant) which attacked into a 7/5 spirit token. (The token was equipped with a Slayer's Plate, had a stat bonus and vigilance from Gideon's ability, and I think a Serene Steward buff too. I don't remember where the stat bonuses on the It That Rides came from.) My It That Rides as One attacked into the vigilant Spirit, killing it and dealing trample damage. However, only 5 damage was dealt, and I only gained 5 life: 2 to the spirit token and 3 to my opponent. The spirit token was killed (correctly) despite the Battle Log showing it taking only 2 damage. 

Expected result: The token should have been killed taking 5 damage, my opponent should have taken 3 damage, and I should have gained 8 life. 

https://imgur.com/a/kAfOp