The combination system seems not to always work, i tried to combine 3 tier 1 stealth imps and it didnt work, and the same happened when i tried to get a second turtle goblin, they wouldnt combine. other than that, fun game!
yeah, thank you for the catch I saw this bug once when my friend tested the build, but I didn't had a time to investigate it I hoped that no one would encounter it. So you won the lottery here :)