Brakes slipping over bumps

Hi guys,

I have a 98 XJ w/ ABS and when I drive over bumps with the brake pedal depressed ~1/3 of the way, it's like the brakes slip or release and the pedal goes soft and then they quickly come back to normal braking. It doesn't seem to happen when I have a firm press before the bump. And it also happens when only one wheel hits a bump. It can be surprising and adds a few feet to my stopping distance.

Anyone else notice this? I can't seem to find any other mention of this symptom. I have a couple thoughts of possibilities, but I would like to hear from you guys first.

Definitely sounds like an ABS problem.
Pull the ABS pump relay, under the hood, and see if the problem goes away.
This is what I did with my 97 XJ, when the ABS light came on and I couldn't quickly solve the problem. Also pulled a fuse to turn the ABS light off.
I must admit I didn't try very hard to solve the problem since the D35 was about to be pulled and replaced with a newly built 8.25 axle.

Honestly it sounds like one tire is momentarily locking up over the bump (not in contact with the ground) and activating the abs. Shocks in good shape? Or like above just deactivate it.

i once had a ford that had a bad wheel sensor. would only detect motion after 7mph so during normal stopping once you slowed down to 7 the abs would kick in.