Bugaboo handle issues can be caused by faults in either the release buttons or the hubs and the first job is to try and diagnose the part causing the fault.
I'll describe how the locks work then go into more detail on each part.
Two aluminum lock pins sit in channels of the inner hub and extend into pockets in the outer hub, locking the hub. These lock pins are retracted by the rotation of a plastic disk connected to the ends of the lock pins by two small plastic pins on the disk.
A wire rod that clips into the disk and runs up the handle to the release button rotates the disk when pulled up buy the release button.
There are two versions of the release button.
The older pull up knob type and the newer rocker button type. Both versions pull up the wire rod via a plastic block clamped to the wire rod. A compression spring sits above the plastic block keeping it in the downward lock position till upward moment from the release buttons unlocks it.
A lot of locking problems are just poor lubrication so before you start opening parts, get a can of Silicon Spray (Bugaboo use to include a can in their maintenance kit).
Any hardware or Gas Station will sell it.
Don't use Oil based lubricants like WD40 the main reason being they stain fabrics. Remove the seat unit and lay the stroller on its side faulty hub down.
Now look on the inside edge of your handle where it joins the plastic hub, you'll see two slots in the plastic hub and a wire rod in the lower slot.
Spray into this slot so lubricant flows down inside the hub.
Now wipe off excess with a paper towel and work the release button a few times.
If you are lucky your handle now works.
Then we have to see if the fault is in the hub or the release button.
Press or pull the release button while watching the wire rod in the lower slot.
It should move 6 to 8 mm.
If there is a resistance to this, the hub is at fault.
If the rod seems to move freely but the hubs remained locked try pulling the rod a bit further up with a small pair of pliers.
If this releases the hub you have a release button fault.
If the hub is still locked the fault is in the hub. Release Button Repai
The old pull up release button is easy to open, a single Phillips screw holds it on and in being so simple makes it unlikely to be your fault.
The rocker button release is not so easy.
The left side is part of the brake lever assembly.
Remove the two Phillips screws and the inner half of the assembly will come off rocker button attached.
The brake lever, inner brake release button and spring will be loose so carefully place aside in a small container till ready to reassemble.
The right side has no screws it just clips together.
Use a small flat blade screwdriver to pop the joints on the front and back edge's, the inner plate with rocker button attached will come free.
There is a metal plate sitting over the hole the rod is in.
Take time to remember how it fits in the hole and the angle you take it out.
This will make putting it back much easier. The wire rod runs though a white plastic block clamped by an inner metal block with two inset hex screws.
The hex key is 0.05 inches or a 99-20 if you have Xcelite hex drivers.
Adjust the rod by pulling a few mm though the block and re-locking.
Don't take up any more then required to unlock the hub other wise the locking rods won't fully engage in the hubs when locked.Hub Repair
1/. Remove the capped star lock washer. This is the hardest part of the job. Most people try to leaver this off in the hope of re using. This can mark or damage the surrounding plastic, second problem is star locks are not intended for reuse and will never hold as well as when first used. I supply a free Dome with the other hub parts I sell but if you are getting your hub parts direct from www.shapeways.com/shops/bugabooparts . You will need to find your own domes or reuse the ones you have. To find domes Google "Bak-Fin" or go to www.bakfin.com/starlock/domedcap.html you need the number 8 Domed Star Lock email them to find your local supplier or just check out your nearest supplier of industrial fasteners.
If replacing the domes the quickest way to remove a capped washer is to carefully cut a slot in the dome with an angle grinder and then use a large screwdriver to carefully prize one side up so you can fit another screwdriver under the star lock.
Note the walls of the aluminum hub axel are thin and easily distorted,make sure you only lever the capped star lock and not hub axel.
Use one screwdriver as a support and another to lift off the capped star lock.
If you need to save the domes for reuse use a small 1 inch painters knife to protect the plastic and only work inline with the handle as there are ridges on the sides.
Some Bugaboos now come with an extra plain Star Lock washer under the Domed one. These are set into the hub and are a bit of a pain to remove. Just pry around the tabs with a small screwdriver. The good news is they are reusable just tap them back on after your repair.
Note it is best to open and repair one side at a time, so you are moving and flexing one side of the handle does not dislodge parts in the other side.
The hubs and disks are mirrors of each other and not interchangeable the locking rods are interchangeable.
The side with the brake lever is left The Bugaboo parts will have an "L" after their serial numbers.
2/Before ordering parts check the hubs for wear.
If too badly worn or damaged you will have too much movement in the locked position.
The Frog, Gecko and Chameleon use the same plastic hub so find another frame to salvage hubs from.
They are held in by a single aluminum rivet.
3/The inner hub has three parts the two locking pins and the disk. The locking pins can only be replaced if broken, either by ones salvaged from another frame or new copies. I prefer the copies as they have been cut or printed from stainless steel. The disk has two plastic pins that move the locking pins in and out of the inner hub if they have not failed they could at any time after your repair so I recommend replacing them.
You need to either repair the disk by drilling out and tapping the pin stumps for 4 mm Cap bolts then cutting them down to suit.
Or (my preferred choice) have a new metal disk fabricated that will last a lifetime. Now with 3D printing you have more options check out www.shapeways.com/shops/bugabooparts
White plastic disks are $15.00 or stainless steel disks for $30.00 and Locking pins are $15.00 each Shapeways ship to USA & Canada for $6.50 and EU countries for $9.00 the rest of the world is a flat rate of $20.00You can buy parts direct from me at the same pricing but my locking pins are laser cut stainless steel $15.00 and my disks are laser cut aluminum with stainless steel pins $30.00 I include a free Stainless steel dome but shipping from New Zealand to USA / EU is $33.00 unless you go standard parcel post $15.00
Reassemble handle locking hub and check operation.
If wire rods seem to be in the incorrect position, loosen the top plastic fittings where the handle extends from by removing the small self-tapping screws (note I'm now finding some frames now have pop rivets,drill them out and replace with self tappers) and wiggle things into alignment.(I use a small amount of the silicon grease used for taps to give a smooth action)
If all is working well fit the new capped star lock on the hub shaft and tap home. To protect the dome finish I use a large socket from my socket set and an old rubber washer from a toilet cistern.
Repeat operation on the other side.
I can't emphasize enough the need to keep Bugaboo hubs well lubricated with silicon spray.
They have to endure incredible forces from the handle.
To give you some idea, a crow bar of the same length can pull six inch nails out of hard wood!
You can contact me at firstname.lastname@example.org