Give 'em a break! The movie was made in 1960. Hardly fair to hold them to today's special effects standards! There was no nuclear bombing of London in 1967, either . . . should that count as a "slip up"?
the morlocks are one of my favorite parts of the movie because of their costumes. during the underground scene where the eloi's are fighting the morlocks you see one morlock is caught on fire. you can very clearly see that he is wearing a very bulky fire suit. also, there are morlocks whos paint smudges, and their costume fold. its pretty funny.