What is going on with zillow?

I have been following the ups and downs of my two properties on Zillow. However, a couple weeks ago, to my surprise both homes were valued at X amount of dollars one day, and poof! over the weekend one of them went down to the price I paid in 1988 when I first bought it. The other dropped considerably as well. Funny thing is, one of my properties is a half duplex. My best friend owns the other half. Zillow shows her half as having been valued at nearly 13 million dollars (!!!!) in June of last year, and down to just 12 million earlier this year (!!!!!). A 1200 square foot half duplex in the bowels of my city....I couldn't help but chuckle. Seriously, someone must've fallen asleep on the keyboard! Back to my property, on Friday it was valued at $168K....on Monday, $119K. My property in Florida was valued at 84K on Friday...on Monday, it was down to 74k. Hmmm. Has anyone else noticed this? Unfortunately, there is no "contact us " option for Zillow.