I've used it. I still use the bucket because it seals nicely and easily but for other salts. I would recommend mixing the dry salt very well before using it as the way they put the salt and chems into the bucket does not promote an even mix. Roll it a bunch of times before your next use.
If that doesn't work I would question the scale your using. Are you sure it's dKH
and not Meq/l?
Finally, if that still doesn't solve your issues, dosing magnesium may help prevent calcium carbonate from forming and precipitation gout of solution. That would raise alk