Maybe the OP shoots in D-log where the minimum ISO is 400. OP did not really provide enough info ie. ND type if any at all, focusing method etc. for us to be able to help
turn your iso down to 100 in bright sunlight. then shutter would have been 1/60 to give you buttery smooth video at 30fps. use a high quality ND filter to bring aperture down to F8 or F5.6.
IMO, this should give you best video results. if not...
And pls excuse mine in replying to a question you didn't aim at me ! :) We didn't become atheists. All humans start off that way ! Animals stay that way, and increasingly smaller and smaller percentage of humans being the exception.
And Atheists...
Yup. Eliminate the cheaper, better competition, under the guise of xenophobia, so you can have a monopoly of far more expensive, less capable, patriotic offerings!