I've noticed the same issue recently, a lot. No idea how long it has been happening.
V 3.0.13
Linux Desktop
Syncing to dropbox

Very frustrating to do a LOT of researching and choosing which product I want, making notes of it, and putting in links. Just to come back later to do my shopping and everything I typed is gone.
I soooooo don't want to have to switch back to OneNote

eta: just updated to 3.1.20 - will see if keeps happening