Today in the morning I had some sayer, pitted dates and some medjool ones. Shortly after, I had a really fast pulse and had somewhat of a reaction (some sleepiness, brain fog, etc.)
Later in the day, on two occasions I just had some Medjool dates and was fine, no sx. (I like dates  ).

The ingredients on the sayer dates is only sayer dates and the package says "natural". They were fairly soft and stuck together.
(The Medjool dates was the only ingredient on the other one, they had pits, were drier and did not stick together).

I looked up how they pit dates and the only thing I could find is that they may steam them beforehand.
What the heck?  

Edit - Okay, I did a little more digging and I am thinking the sayer dates contained a preservative such as ethylene oxide or sodium metabisulfite to keep the dates softer. The medjool dates specially say "no preservatives"...