
It seems to be some white suspended particles. I just installed a new Mini reservoir BestCup softener yesterday. I suspect these cloudy particles are somehow related. After about 6 shots (basically emptied the boiler), it cleared up.
Another good reason to skip the reservoir softener and use 50/50 RO water and tap ! (And especially since my last Mini softener cost me $35 !!

So, if you decide to use the softener, I suggest the following
1. Soak the softener in a glass for a hr to activate
2. Install in reservoir, add water and pull 4 water shots. Leave overnight.
3. Next morning, empty reservoir, refill with fresh water, and pull 6 water shots into a clear glass until no white residue remains.