Sticky tambour doors  

First, you've got to find where
they are binding and then determine why. It could be simply that crud has accumulated in the grooves and needs to be cleaned out. Worst case scenario involves warped, swollen or shrunken components, delaminating backing canvas, or other damage or deterioration that would require some disassembly to diagnose and/or repair. The usual protocol begins with inspecting and cleaning as much of the grooves as you can access without removing the back. Paste wax is the normal recommendation for lubricating sticky drawers and tambours with carnauba being the hardest and most durable. Avoid spray lubricants.
Good luck!