Cannot backup WhatsApp to iCloud
I'm trying to backup my WhatsApp chats to iCloud within the app, and it gets stuck every time at 107.1MB, or 2%.
Things I have tried/issues I have ruled out:
-- I don't use iCloud for anything else (I backup my phone to my computer via iTunes), so I have all 5GB free. The total size of my WhatsApp backup (without videos) is 3.85GB.
-- When the upload hangs, I have gone into Settings > username > iCloud > Manage Storage and deleted the (unfinished) WhatsApp backup. This allows me to start the backup over in WhatsApp. But it always stalls at the same point. I have done this several times.
-- I tried allowing WhatsApp to include videos. This raised the total backup size to 5.6GB, which is too big for the 5GB iCloud allotment. It started the backup anyway...but then it stalled, at about 16MB this time. When I deleted that backup, and tried again without videos, it once again stalled at old familiar 107.1MB.
-- I have restarted the phone. Including the hard reset.
-- I have updated iOS -- I'm now on 13.5.
-- I have turned off iCloud Drive and turned it back on again.
-- I have logged out of iCloud and logged back in again.
-- I have reset network settings.
(I'm only trying to backup WhatsApp because I'm trying everything under the sun to fix this issue: https://discussions.apple.com/thread/250814508?answerId=252643012022#252643012022 My push notifications have stopped working for several apps, and WhatsApp now only loads messages if I actively have the app open on my phone. Also the case for several other apps, but I use WhatsApp the most.)
Any suggestions would be welcome -- thank you! I'm very frustrated.
iPhone 7, iOS 13