When using Villager trading hall design (utilizing detector rails) the detector rails get 'stuck on' regardless of whether there is a minecart there or not.
In addition, when a minecart is dropped from another rail onto a powered rail, the card does not move until interacted with.
(in this example, the minecarts go from the holding pen in the picture to a line of powered rails two blocks below when a button is pressed. the minecarts do not move when dropped)
Please check if this is still an issue for you in the latest 1.14 development snapshot.