I just noticed the details of several contacts disappeared from my contacts app. I noticed because my mother sent me a message and only her number was displayed, instead of her name. Then I went into the contacts app and her entry was there, but it was completely empy, no number or anything showed up.
As of now I confirmed the loss of about 10 contacts (because WhatsApp does not display their names anymore) but of course it's impossible to tell how many more have lost all their details.
Logging into my Microsoft account it seems that all the details are there in the corresponding contacts, so it's the app or the os in the phone that are not capable of finding them.
I tried going into the contacts app --> manage contacts --> sync contacts, but nothing changed.
I am sure I hardly need to stress how unacceptable this is.