I see why the new witness list is not saved, it'll be fixed in the next version.
In the meantime, I updated the main hub to enable catchup with old witness lists. Your wallet should start syncing if you open it again.
No new version of the wallet available yet? The wallet is being updated and I can already see some Obytes in the wallet, as well as other tokens such as Silentnotary and Titan Coin, but unfortunately I don't see any Blackbytes yet.
No new version, but your sync issue appears to be already resolved.
You won't see Blackbytes by continuing the sync. By their nature, they are a private asset and are stored only in your backup.
However, the wallet synchronises very slowly despite a fast fibre optic connection and when the CPU is not under load, could it be that I am not connected to all witnesses?
The bottleneck is usually in CPU or disk speed, not in network connection.
You don't need to be connected to witnesses. In fact none of the witnesses accepts connections.
No idea where the syntax error comes from, maybe the backup is corrupt. You can install an older version of the wallet from
https://github.com/byteball/obyte-gui-wallet/releases released at about the same time when the backup was made, and try to restore into that version. Before installing an old version, make sure you uninstall the current one and rename the data folder to get it out of the way.
I will only try if I have no more Blackbytes, but after successful synchronisation I will immediately create a full backup again.
As I said, sync won't recover them. They are only in your backups.