Man, I had one of those, a great device for a quick setup for drum brakes, but that way back when I used to run 11 x 3 inch cop car drums on all four corners of my 67 Plymouth .
Satellite.

That might be in the bottom drawer of my tool chest. (Read in junk drawer)

 

Check the front brake lines, a panic stop can over stress them and cause them to become weak and swell close to the caliper. That would cause a softer pedal.

 

I'm assuming you mean brake hoses

 

Yup, I meant the rubber hoses going from the hard lines to the calipers.
Sometimes you can see them bulging at the end.

 

or... if there was air in the HCU portion of the ABS module, it could explain it.

The electronic bleed might just need to be done again. When I used to to do low-level motorsports(different vehicle with ABS), this was not unusual. If the system is opened, air gets in, and it can go to the ABS module. 1 panic stop and it goes out into the previously good system.

I had the good fortune of regularly braking hard, so this surfaced fast... lol

It's an idea, at the least. Hope it helps.

If I bleed brakes, I always exercise the ABS. Some electronic units don't.