After the update to 1.39 I got camera jitter problem with UFPS, but the script execution order doesn't help. 
 Once my character walks up a staircase everything starts to shake and 
then gradually returns to normal until I try to walk up the stairs 
again. Also, the jitter occurs while walking on the flat surface, but 
not as bad... Furthermore, I found that the jitter disappears if I 
have the Camera&Controller object in the scene, but once I delete 
it to use Player Prefab, the jitter is back.                
                             
        
Comments
The source, I think, is in the MainCamera script. Open it up and change the LateUpdate () function (line 364) to Update (). Does that solve it?