Did a quick search and only found old issues relating to this.

Command Block Chain Conditional Always Active
/execute @e[type=armor_stand,name=VexBot1] ~ ~ ~ detect ~ ~ ~1 air 0 /teleport @e[type=armor_stand,name=VexBot1] ~ ~ ~1

Output: [00:43:58] Failed to execute 'detect' as VexBot1

This command block was executed by means of a trigger.
Was working in 1.11.2