Factual error: While bidding on eBay for the steering wheel, Vanelope tries to up the $350 bid by bidding $1,000. This scares off the real bidder, but Ralph and Vanelope don't understand how eBay works and bid against each other until they win with a $27,001 bid. That's not how eBay works. Vanelope's initial $1,000 bid wouldn't have set the high mark, but would simply have been her maximum bid in case the other bidder kept increasing his bid. The current high bid would have increased by the increment amount until it reached Vanelope's max bid. Now, it could be that the system recognized Ralph and Vanelope as separate bidders and that's why it let them keep upping the max bid. But, if the system had responded normally and simply increased Vanelope's bid to $355 with a max of $1,000, they might have realised what was going on and not started bidding randomly.
Factual error: The rabbits are underneath the landrover, and they get shot out the back whilst holding on to the axle. Land rovers have an enclosed axle with a hub enclosing the diff, so this would not be possible.
Factual error: When Elastigirl receives her new bike she discovers it's electric. Later, when she is rescuing the train, the bike hits a mountain and is destroyed in a fireball. What is making the fireball? It's electric so there is no gasoline/diesel to make a fireball, and a lithium explosion doesn't look like that. (00:33:30)
Factual error: The female Frankenstein tries to set Dracula up with during the wedding reception is referred to as his "right arm's cousin" but the big arm that looks like Frankenstein is her right arm. (00:08:10)
Suggested correction: Frankenstein wasn't saying she had the other half of his right arm (i.e. his left arm), just that the 2 arms came from 2 people who were cousins.