They've got a billion-strong userbase and yet the Android app still dumped literally every attachment I received into my camera roll until I manually added '.nomedia' files in the right places.
And, oh man, the API for businesses is a Kafkaesque nightmare. Maybe it was good before it got Zucked, but I had to fight with their support for over a week to get an automated ban-hammer overturned... only for it to get auto-banned again two days later. We hadn't even deployed the damn thing yet!
That works fine (and is in fact easier than remembering the exact album) when I get to pick and choose exactly what I photograph/save, but it became borderline unusable once WhatsApp started vomiting hundreds of stupid GIFs and throwaway screenshots into it.