Kinetico Q237 5-10 second burst of salty hard water during regeneration

As the title states, I have a Kinetico Q237. Every time I'm in the shower when the unit starts a regeneration, I can taste and feel salty, hard water coming through the pipes. This lasts probably anywhere from 5 to 10 seconds. I've taken apart the head and completely cleaned it out. I've done my best to clean the sediment pre-filter. I've taken apart the brine valve assembly and cleaned it out. Everything seems to be good as new. I bought this unit used on Marketplace maybe 5 years ago and it's done this since day 1 of me owning it.

Any ideas as to what could be causing this? I'm thinking the pressure to the unit is fine. I don't think the filter is dirty enough to be causing that much of a restriction, but I guess you never know. I've looked at detailed Kinetico head operation diagrams online and I'm trying to figure out where in the regen process that hard water + brine could be allowed to "cross over" into the soft water outlet valve. Any input would be much appreciated.

 

EDIT: Turns out the salt is not coming during the regen cycle. It actually happens right before the regen cycle starts (at least the noise I associate with the regen cycle). Brine is not being drawn at the time this is happening, so it's got to be brine that's already in the tank. I'm thinking it's something to do with brine not being completely washed out, but the water flow out of the drain during backwash does seem to be high enough pressure. Hopefully this will offer a clue to someone more knowledgeable.