When Peri enters the Tardis after the Doctor's fishing trip, she is wearing different shoes.
No explanation is given why the Second Doctor and Jamie both look so much older than they did when they stopped travelling together at the end of The War Games (1969). In reality, 16 years had passed.
When Sra. Arana asks "Who's there?" in Spanish for the second time, she says "¿Quién está?", which is a phrase hardly used in common Spanish. The most correct phrase would have been "¿Quién es?" or "¿Quién está ahí?".