What is used as the balancing weight for the lens? I see DJI specs state you need it?
For most of the lenses that are usable on the X5 you should add a filter for weight balance AND to control light. During normal daytime shooting you want a ND filter of 2-4 stops to allow you to set the shutter speed to 2X the frame rate and in order to do that without pushing the f/# too high you need to reduce the light coming in.
When it's darker or when you wish to shoot stills you should still use a filter for balance but in this case a UV filter that doesn't cut the light very much is preferred. For stills you want fast shutter speeds.