hi guys, I think it has to do with whatsapp. I have had issues with whatsapp in the past, so i refused to update it
So when this issue of 'contact manager has stopped' started, i saw this article. I quickly cleared data and cache of whatsapp, then updated whatsapp to the latest version. When I started the application, it asked for my phone number (normal setup) and verified it, then asked me to select to restore backups of the chats. I skipped the restore (this is important).
I have whatsapp but all my chats are gone. So memory is free. And contact manager works fine. By the way, my phone is rooted.
I suggest you uninstall whatsapp completely. Then re-install and do not restore any backups, just use it fresh. And clear data of other apps too like, play store, browser, etc.
Hope this helps