I know my Electric Brakes are 'grabby' when I first start using them on the trip. Here at the house I hook up and test safety lights and all then start leaving the housing area.
My trailer brakes are very 'grabby' doing the initial tests to see if they are working.
I have a full stop zone about 400-500 feet up the road after we start out still inside the housing area. I will use the manual slider for the trailer brakes to stop both and trailer at this stop sign...
All seems to clear up for me after doing this...
My Electric Brake controller is a built-in FORD OEM Brake Controller...

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I suspect this 'grabby' condition is due to accumulated moisture on the Brakes while sitting at the house a long time not being used.
A side note for my 4WD Jeep - This grabby situation reminds of the few times I replaced the clutch in the Jeep manual transmission. I always had this same 'grabby' condition and would pop a few heads until it wore-in and was smooth to use. I have on several occasions nosed up to a tree and slipped the clutch at high RPMs doing the so called burning-in of the clutch. Sure got a few strange looks from folks while I am trying to push this big tree over with my trusty ole Jeep haha... Smoked up the Jeep clutch pretty good doing this but the end result was always a smooth operating clutch after that. No telling how many miles of operations was removed from the clutch doing this haha...
Roy Ken