I have exactly the same problem. Thanks for the link, but I wonder if this synchronisation issue is being addressed?

Healthy blockchain should be easy to sync without snapshots. Right now, it looks like snapshots of the ledger are the only way to sync this. Without them, the chain keeps going back and forward, gets some blocks, then rewinds back. I though that is just my node, but it seems to be a common issue.

Isn't this a serious issue to address?

P.S. One additional small question: what is the right way to do a backup? Is making a copy of "privkey.der" enough, or other files may be needed too?