Skipping frames with panning video sideaways after export

I don't know for sure, but you may consider trying 1-pass encoding at a higher bitrate. 50fps in 10-12 Mbit with considerable movement may be the source of your problems.

I noticed that the source footage was shot at 50 frames per second. Is this intentional? For normal speed playback, you typically choose 25 fps in Europe. Only if you wish to use the footage in slow motion (i.e. tell Premiere Pro to interpret 50p footage as 25p, thus half-speed playback), would you choose to shoot in a higher framerate.

But the most likely source of you troubles may have to do with whatever your DJI chooses as shutter speed. The higher the shutter speed, the more likely movement (e.g. your pans) will appear choppy. A general rule for normal movement is that your shutter speed is kept to 2x the framerate: for 25fps this means 1/50th shutter and 50fps 1/100th. In order to compensate the amount of incoming light, cameras set to automatic modes will go for higher shutter speeds, such as 1/250th or even 1/1000th. This typically results in video-like footage.

Instead of using shutter speed as a way to change the incoming light, it's much better to use your aperture (which affects the depth of field) or putting sunglasses in front of the sensor. The latter is called Neutral Density or ND filters. Poor quality ND filters may result in unwanted color shifts, though, so it's good to test them out before use.

Hope this helps.

That is a camera pan?  Not done in post?