Other mistake: When the children arrive in Blackpool, Emma tells Jake that loop entrances can be anywhere and that "the one in London is in a subway tunnel", but on the map of all the loops they were viewing previously inside the boat, there was no marking of a loop in London.
Other mistake: When the Hollow is approaching Miss Peregrine by the shore, it doesn't cast a shadow when it's invisible. But as seen several other times in the movie, Hollows cast shadows when they are invisible.
Chosen answer: At several points throughout the film, there are instances where her powers of air are used only as a plot device, so the extent of her powers is somewhat unknown. Therefore, it is possible she is able to make herself sit on the cart without floating, but other times isn't.
Amina Thommesen-Kähler