rainsoft q2 hard water

sounds like the poppet isn't sealing under the triguard. When you put the bypass in the soft water position, is the ball in the triguard( clear plastic thing that the line coming from the salt tank attaches to) at the top or bottom? When it's not regenerating it should be at the bottom. The only time there should be suction is during step 5 and 7 of the cycle. Water is put into the brine tank during the first stage of regen. After step 5 there should be only a little water in the triguard until the next regen.

If you put it on bypass and it starts filling the brine tank , it's in the brine fill part if the cycle and the water level is equalizing,

Yep, check the tri-guard and make sure you re-installed the poppet properly and that you did not over tighten the assembly and crack the base of the tri-guard. A hair-line crack will cause the problem you describe, but it will also leak water. Make sure all of your fittings are lined properly threaded and finger tight. Did you inspect/replace the shut off tabs? A bad brine tab can contribute to your problem.