When the first victim, Monica, gets bitten by the invisible snake on her chest, she opens her shirt and the marks in the middle and straight across below her collar bone. When they show her dying on the floor, the marks are diagonal and closer to her left shoulder.
Artie used a Tesla on Steve after Claudia neutralized the Hendrix guitar. It was established in the Pilot that a Tesla hit wipes the target's short term memory: so, Steve should not have been able to remember anything of what happened inside the museum.
When Pete is at the fire station and fits the special nozzle to the fire hose and goes to save the girl in the phone booth, the hose is not charged. When he rushes away from the station and the scene changes to show Pete using the fire hose, it is suddenly charged.
The type of guitar Jimi Hendrix was best known for playing, and the type he burned at both Finsbury Park and later at the Monterey Pop Festival, was a Fender Stratocaster. The guitar depicted in this episode is an imitation Stratocaster, as can be seen from its headstock. Additionally, although Hendrix (who was left-handed) played right-handed Stratocasters held upside-down, he strung them in the left-handed fashion, as any other lefty guitarist would. In the closeup of Claudia playing Hendrix's alleged guitar, just before Artie scolds her, it can be seen that the guitar is strung right-handed.
At the second murder scene Steve tells Pete that Forensics say the victim was stabbed 23 times, with 23 different knives. But the body is still in place against the wall. Such details would only be known after autopsy.
When Agent Jinks performs the classical Buddhist finger gesture, Karana mudra, for warding off evil. he touches his index with his thumb. However the proper way is to gently curved downward the middle finger so it touches the tip of the thumb forming an oval figure.