Battle Beyond the Stars (1980)

Revealing mistake: After Sador has Nestors arm removed and it shows him on the bridge, his real arm is obviously seen hidden underneath his clothing.

Revealing mistake: When Caymans right hand man throws his spear through the bodies of two enemies, you can see that the part of the spear sticking out of the second guy isn't remotely in line with the spear going through the first guy.