I found a bug with a dragon from 4 taverns 5/6 that does not trigger a 1/1 dragon with an end-of-turn effect. And yet this combination starts to work if you throw reverber drake on Upbeat Frontdrake.
It would help a lot if you said the actual names of the minions.
[Edited] I’m assuming the 5/6 one is probably the Efficient Engineer but it would help if you could confirm the name of the other minion, Vattghern. and the second one is likely the Upbeat Frontdrake.
This is now added to the Known Issues thread. 
Yes, that’s right, I wrote a post before going to bed on emotions, I didn’t indicate the cards. It’s my bad.