I am having very similar issues. Anything I do on the Mac app doesn’t sync anywhere else. I also had the terrifying experience of typing in a note and then watching in horror as the constant sync would just erase what I just wrote. It’s awful.
I’m a long time premium member and I submitted a support ticket, but they’re saying the wait time is 10-12 days. They’ve also shut off chat completely. I’ve tried tweeting @evernotehelps, but so far, no response. I’ll let you know if I hear anything.
i went ahead and installed the legacy version yesterday. After a month of battling with the horribly slow and buggy new interface, the old legacy version feels so smooth and fast. And most importantly, everything still seems to be syncing.