Other mistake: It is said G. Callen has lived in 37 foster homes between the ages 5 and 18, the longest ever having stayed in one is 3 months. 5-18 is 13 years, meaning even if he had lived 3 months in EVERY foster home, it'd have to be a minimum of 52 foster homes. Since 3 months was the longest, it is logical that the others were shorter therefore the number would have had to be much higher.
Suggested correction: It was never said he spent every day from age 5-18 in a foster home. He was returned to social services after every failed family and likely had to rot there until another family was assigned. He also had several stints in juvi. So the 37 foster homes within 13 years isn't necessarily a mistake.
Other mistake: When Summer is fighting the Grinders at her wedding, she throws at least four kicks that completely miss her enemy, yet they react as if they were hit with great impact.