An old Coinbase alert suddenly comes to life

This morning, one of my old price notifications on Coinbase was triggered, telling me that ETH was now below €550!

Was Ether finally correcting?

Initially, I was kind of shocked, but at the same time fascinated. Ether has held its value over €800 really well lately, but it shouldn't come as a surprise if it suddenly started to get affected by the recent decline of the Bitcoin price.

Interestingly, the graphs are all good

I checked the graphs, but everything looked normal. The price had definitely not fell down to €550 during the night. I checked the alert again and found that the alert had indeed been triggered today!

Maybe someone performed one single Ether-trade below €550, triggering the alert? But if so, why doesn't it show as the day's lowest value in the graphs?

Did anyone else get suspicious price alerts today?