I deleted WhatsApp a while ago so can't say right now. It is a pretty mature app that hasn't added big features in years I think, so I wouldn't expect a lot of bugs in it, but take a look at their version history on App Store, there are plenty of purely bug fix releases only this year.
I find that a very strong claim, is it rhetorical or meant literally? If the latter, what can you find in (say) whatsapp* ?
(*: aside from messages delaying or appearing out-of-write-order, which are probably backend bugs inevitably arising from its distributed nature)