I had the same problem, with undisssolved particles on the bottom, or like using liquid sand, you forgot to mention the smoky haze that rises up when hot water is added. I spoke to LL who sent a new tub, and after a couple of uses it went the same way. Gave up on it, but might try the other suggestion. I was using on bitches pants or skirts (depending on which breed you have) to help get rid of wee stains.
I didn't want to scare anyone else off
So, with your second batch, did it dissolve properly at first? (ie maybe the problem is the age of the 'crystals')
Yes second batch was OK for first one or 2 tries, then it went the same way - pity the tubs are so large. Not sure if LL have looked into it and wether the powder/ crystals need one of those little moisture absorbing satchets you seem to find in everything !