Keith never gave the commands to prepare a merging, and had the feet and legs form after, not before, the arms and body.
The missiles that impaled Blue Lion are no longer seen when the next shot of Voltron appears.
The rip-claw front paw of Yellow Lion that was fired and destroyed returns to it.
When Keith gives the command "Blazing Sword" (a goof in itself; it should be "Form Blazing Sword"), the Right and Left Arms of Voltron do not connect than withdraw to expand it between them; it is already shown as a dim apparition than materializes in the Right Arm.
At the start of the conference table scene, Allura's casual outfit is miscolored as her flight uniform.
Haggar's robot is repeatedly referred to as a copy of Voltron, despite little if any resemblance.