Well, it’s happening again!! I believe the pistons or “cups” are not distributing even pressure. Would rebuild help? How far can I go with “cleaning” or resurfacing the cups? Or, are the calipers not getting good pressure? I’ve bled the system many times.... this is frustrating to say the least!!
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It has been happening to my bike also since it was new. Braking at low speed I can feel an ABS like vibration but I never paid much attention as it is happening seldom, rarely. In 4 years and 60.000 Km maybe it has happened 10 or 20 times.
MMC i had an identical situation on my cb919, it was fine when i got it but i think putting it away with wet disks got it started, tried to clean the rotors but never got it cleared, lived with it for some time and it gradually got slightly better and it felt that over time the patch grew longer to finally cover most of the surface by gradually applying the brake, it felt like the "resin" that binds the brake material together ( i don't know ) covered more and more of the surface, it definitely improved the friction until i replaced the pads which cleared it instantly, no more pulsing or at least very light and not very noticeable.
To isolate the problem you could swap one caliper inside with the outside pad, if that makes no difference swap the other caliper, swapping this way will at least point out which pad is pulsing the brake.
Not knowing the history of your bike it may be time for a different brand of pads, it does not add to the driving pleasure does it?