Seat wont lock into position as white buttons wont pop out

Silicon Spray and brute force is the simple solution. Taking the screw out of the back of the seat locks is the tricky one with little parts and springs popping out.

With the seat unit face down push down inside the lower leg unit with a screw driver, The white button should pop out. If it does not either the button is stuck or the locking splines on the outer sides of the button unit are not sliding freely into the spines of the outer ring. When you push down with the screwdriver your force only pushes the back of the button unit. It is the inner spring that has to move the white button and the locking splines so any burrs or roughness can stop its movement. www1.fixya.com/support/r7805137-fix_bugaboo_white_seat_buttons

The chassis must be fully opened out and the handle locked in position before the seat / bassinet frame can lock down on to it. The seat / bassinet frame is the safety lock keeping the frame ridged. You should see a square hole (made by two half squares from adjoining hub disks) at the top of the chassis hub assembly when fully open. A square pin under the seat frame must engage into it and the white release button must click. Your Bugaboo will not br safe unless this happens and you should contact the seller to help.

Not sure if you mean the handle is locked up and won't move or the seat is locked up and won't move? The front and rear wheel units are locked by the seat unit. The handle has two release buttons that have to be opperated at the same time to release the handle. The seat tilts by pressing the large white buttons on the side. Let me know what part is not working and I'll try to help.

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common problem www.buggypitstop.co.uk have the answer.

middle seat belt shouldn't have anything to do with it. The seat locks down for stowage in the rear cargo area. you can pull the release handle on the back of the seat to release it back into the up position.

call bugaboo customer service (1-800-460-2922), give them your stroller's serial number, and they will mail you the replacement kit (the new round buttons) and instructions for free and very quickly - I had the same problem and was very satisfied with how it was resolved.

My daughter has just brought me a Bugaboo which is 25 months old (one month out of warranty) and after several hours work I have figured out the problem.
The reason that this seems to occur after a year or so is, I believe, related to the fact that the housing in which the white button sits is made of thermoplastic and is not dimensionally stable. For the button to work properly both the circular hole in which the button sits and the button itself must be circular and the button must be very slightly smaller in diameter than the housing. If either of these are slightly distorted the button will stick.
The other thing to know is that when the cradle is off the chassis the button will always be in the 'in' position. What pushes it out is the pressure of the part of the chassis on which the cradle sits when you push the cradle onto the frame (you can demonstrate this by getting a screwdriver or thin dowel) and pusing down on the plate within the socket on the cradle that sits on the chassis - when you do this the button will pop out and when you take the pressure off it will pop in again).
If when the cradle is attached to the chassis the button is not out, give it a few quick sharp presses on one side to make sure it isn't binding on the plastic within it sits.
This should releases it.
The cure? You need to dissamble the button assembly and spray some silicone lubrication or similar and make sure the various parts are working smoothly. Also you need to check to see if the white button is binding on its black housing. If it is, then carefully use some wet and dry paper or similar abrasive on the circumference of the button until it stops binding
Having figured out how this works I have to say that I consider the mechanism to be a very poor one considering the price that is charged for Bugaboos. If they took a little more care and made sure the button and housing wouldn't distort with age and bind, the problem wouldn't exist.
Hope this helps. .