Continuity mistake: Elisabeth Shue is talking to Homelander by her car. As she gets her baby out of the car, she says "can we please just talk later" and has a muslin hanging over her right shoulder, turns around, and from the reverse angle the muslin is bundled up in front of her, not over her shoulder at all. Then the angle changes again and it's back where it was before.
Glorious Five Year Plan - S3-E4
Factual error: The Boys use a Dodge Sprinter to drive around Russia. In Europe and Russia this Sprinter was only sold through Mercedes-Benz.
Continuity mistake: Whilst Neuman is having lunch with Hughie, when she asks "How'd surveillance go with Termite last night", she has her fork placed in the salad bowl. When the shot cuts to focus on Hughie, the fork is now in her mouth and then she lowers it back into the salad bowl. (00:17:48)
Plot hole: In Russia, Soldier Boy is shown heading to the airport, He wanted to get to the US and start his revenge against his team. Problem is: he has no documentation and money to take a flight. Even if he stole the money somewhere, still would be impossible to travel without the proper documents.
Proper Preparation and Planning - S2-E2
Continuity mistake: Frenchie has some decorations on his shoulders, shot changes and when back on Frenchie the decorations aren't there. (00:37:41)
Continuity mistake: Ashley Barrett is first seen behind Homelander, but then in the next shot she immediately jumps in front of him. (00:19:32)
You Found Me - S1-E8
Continuity mistake: When Mallory is holding the binoculars up to her eyes, next shot they're instantly down. (00:14:10)