CleverNote - A sync spinner disappearing is a weak success signal

I'm building CleverNote, and a conversation about someone else's notes app gave me a useful test to bring back to my own project. On Tuesday I asked an Apple Notes user to compare a test note created on the web with one created on their Mac. They later reported that disabling one VPN feature stopped the endless syncing indicator. Their next update said syncing still became unreliable; disabling a second feature appeared to fix that too. Those are their observations, not a bug I reproduced. What I took from it: a test shouldn't end when the interface stops showing a problem. I'd want to edit a note, verify the exact new text on the other device, then repeat after leaving the app and coming back. That's a test I want to apply, not a reliability claim about CleverNote. What failure have you caught only after the UI looked healthy again?