Wobbly lines on static camera videos Hoping this is the right place to ask this and that what Im asking isn't nonsense.

I record some top down videos of board games, the camera is on a boom arm fastened in place overhead pointing down (I can't work out a better way to do that at the moment but it works for now and isn't the main issue of this question anywho...), the boards in question have a white grid on them and when I edit and produce the footage I find afterwards that the lines seem to wobble, see here for an example of what I mean if you scroll to 6.47 (as a random point without things obscuring the view).

I'm wondering what the cause might be and if I can stop it happening.

I do have to use the distort tool in fcpx to drag out the edges and rotate things a bit as usually my camera is never centred on the board and so one end has a noticeable slant/narrowing to it as the camera is pointing at a slight angle, could that cause it and if so anyone have any tips or suggestions as to how I can ensure my camera is pointing square to the table? :/

Cheers!
After much help above it looks like its because the camera I was recording on was recording in 50i but the project I had created in fcpx was set to 60p, this was causing issues with the final result as it tried to convert 50i to 60p...

I restarted one of the projects as 25p instead and copied in some of the source video again and a quick repeat of my normal output process (export as mov, use handbrake to convert to a reduced size mp4 for youtube upload) seems to give a much better result (I'm comparing the mp4 on my machine to youtube but there is 0 wobble and I don't think its youtube adding it in) so I think this is the solution, make sure your projects are set to the same fps as the source!

Thanks all