Continuity mistake: "The Time of the Wolf": Robin slays his evil twin and leaves him on the grass near the standing stones. The body then changes positions without anyone touching it. When Robin leaves, its head is pointing to screen-right. But when Marion arrives, Evil Robin has done an about-face: his corpse is now pointing to the left.
Continuity mistake: "The Greatest Enemy": It's full daylight when Robin sends Marion and Much away and stays atop the crag to hold off the sheriff's men. The sky behind him is blue. But in the next moment, as he starts firing arrows at them, there's a setting sun behind him and the sky is red. In the following scenes, we see full daylight and blue skies again.
Continuity mistake: "Robin & the Sorcerer, Part 2": There are two arrows already on the target when Robin's splits one of them. When the target is carried back to the review stand, only the two splitting arrows are there (not even a hole in the cloth where the third should be), and those have somehow moved from the upper right sector of the bull's eye to its very center.