New Notes Occasionally, Mysteriously Disappear. Longtime Bug?

My wife uses Notes VERY extensively and has accumulated literally thousands over the years, from recipes to lists, etc. She is a very organized person. Occasionally she'll work on a note and come back to it the next day only to find it's mysteriously disappeared. It's been a problem ever since Notes was shifted over to iCloud rather than saving locally on the iPhone or iPad. It frustrates her to no end!

Is this a bug that Apple's aware of and just doesn't care about fixing it? It's a phenominal app when it works but it's sadly unreliable. Like I said, this only happens occasionally, maybe one out of every 15-20 new notes or so. And no, she doesn't sync notes with Yahoo or Google. Only iCloud.

Does Apple know this is going on?