Servo Occasionally Jumps/Jolts/Jerks

So, I have a problem. This is the first time I have used a servo in a project and all is not going well. In short, the longer you hold down a button, the higher the angle written to the servo. However, almost randomly, the servo will jump to its end point before returning to the point it should be at.

I am using an Arduino Uno board as well as a number of other inputs and outputs. I have read that the servo library utilises a timer either 1 or 2, however the other library I am using does not use a timer, and the other pwm pin I am using also does not use either timer.

So far my debugging has been extensive. From running example sketches to confirm the servo is running as it should to rewriting elements of my code to prove that the servo can be moved at the same time as operating other IOs. I have put the servo on its own supply and have monitored the data pin with a scope. It seems that occasionally the pulse widens, however I have no idea how to overcome this issue. I have tried putting a capacitor between the power and ground of the servo and yet the problem remains.

I have discussed with my colleagues and they too are baffled. I have spent the majority of my working day trying to solve this issue. Any advice would be greatly appreciated.

You obviously didn't read the sticky, even though it's quite obvious at the top of the forum and says "please read". Please go do this now, and add all those missing bits and pieces of information to your post. Schematics, code, images - the works. Without that, no help possible.