I can confirm this started today, and that is while playing play solo, VehicleSeats and Seats act as if their Disabled property is true. Play Solo is an important part of roblox developing not just for me but for many people, and this inability to sit or drive vehicles is a serious halt to productivity.
How to reproduce:
Create a new place
Insert a Seat and a VehicleSeat
Play solo and touch the seat
Notice that you cannot sit down
???
bug fixed