Since the update pushed last week I have lost the majority of my contacts (Google contacts but they sync'd after the updated and wiped them all away!) And WhatsApp becomes totally unresponsive. Anyone else experiencing this? I hope I have a backup of the 200 or so missing contacts somewhere :(
On the contacts side, have you checked that the missing ones aren't just hidden. This hapened to me a while ago and too me a while to resolve but it's easy.
Go into contacts, select the menu (three lines topish left). Make sure that All Contacts is selected. If that's not it, then I'm afraid they are really gone from your device.
The only suggestions I can make on Whatsapp are the usual ones:
a) Delete the app's data
b) Remove and re-install the app
You will likely lose your app history if you do this - though you could try downloading a copy of the installation files from APKMirror and try installing over the top of the existing installation. However, I really don't know what would happen if you tried that.