I’ve downgraded from NC 2.5.1 due to syncing & performance issues, now sync is working again with the exception of one folder and its sub-folders & files. With each sync attempt, that entire parent folder ends up under the “Not Synced” tab. Those items listed are labelled, under the “Action” column, as “The downloaded file does not match the checksum, it will be resumed.”
I’m not really sure, perhaps there are some old checksums cached. If you set up an account again, it should work. The thing about downgrades is that if there is already stuff from a new feature in the configuration, this could cause problems and in general downgrades are not tested.
In your case, you should ask the developers. I don’t know if the checksum is a partly implemented feature (ownCloud uses this in newer versions), or if there is just an old cache value somewhere (and how to reset it).
I moved the entire directory into another parent folder locally and that clear it up once that sync completed. I then moved it back to its original location and all appears good.
