Ascecion Bug causing lost troops

What you were expecting to happen, and what actually happened?

Was expecting to have 1 more away from upgrading my troop to next ascecion level

What are the steps to make it happen again?

Upgrade a troop to 1 less than than its next upgrade, maybe only mythic specific
Actually tried to replicate this but it happened in 2 cases but didnt happen in other cases not sure what the bug is here but when I was 1 short of a full ascend and tried to ascend with others yet it just wasted them and didnt turn to mythic ( you used to require 2 to complete the final ascend because 1 was so you had 1 troop left )

Maybe someone else has experienced a fail ascend?