Grammatically complete premises need not form a sound argument. The apparent arrangement and the unchanging meaning of the middle term are separate requirements.
For example, “Every lion is an animal; Zayd is a lion; therefore Zayd is a predatory animal” has an apparent first-figure shape, but “lion” may be literal in the first premise and figurative in the second.
Checking the stated propositions alone is not enough. The sense of each logically repeated term must remain constant across the argument.