Using an iPhone SE (1st gen), iOS 15.4, and whatever the latest EN version is (I set apps to auto-update in the background). Used over very fast wifi.
I typed in a long note on the phone last night, one of those classic light bulb of inspiration notes. I set the phone down, picked it up a few minutes later, woke the phone, went to the note, and over half of it was gone. So i retyped what I could remember, set the phone down without putting it to sleep so the note would save. Picked it up again a few minutes later, and again, over half of the note was gone. (If only there was a way to sync the note immediately or at least save it locally in its current state.)
Checked note history in Windows Evernote and it barely recorded a quarter of what I wrote.
I filed a support ticket. I expect the workaround is to use iOS Evernote for viewing only and instead use Apple Notes when on mobile. And to rub salt into the wound, I just last week upgraded to Professional.
The other issue I have with Evernote on ipad and iphone is that notes stop syncing after a while. The only workarounds are 1) restart the device or 2) delete and reinstall the app. I'm frustrated with having to use workarounds so the app will perform its most basic function. Fortunately, the Windows desktop app seems to be mostly solid apart from duplicating notes every so often.