If I try to run a command such as: "/execute @e[score_age=100,name=lightningSquid,type=Squid] ~ ~ ~ summon ArmorStand " in a repeat always active command block, it says "Failed to execute 'summon ArmorStand' as lightningSquid". But if I try to run it manually, it works as expected. Why? Is this a glitch?
You will get this error every time you run the command and there's no entity/target that meets the requirements. So the output says that when the block last tried to execute its command it did not succeed.
About repeating command blocks, that is something that happens, it might be a bug.
Rollback Post to RevisionRollBack
If you want more direct help concerning commands join the /r/MinecraftCommands discord server!