Always when there were problems with synchronization of the wallets in many projects, the first solution provided was the bootstrap file with all blockchain data, mostly ending on the last checkpoint. But to be honest, I have never seen this solution for Bitcoin Core client. When I have used bootstrap files a couple of times, always the synchronization was smooth and took only a fraction of the time needed if I would try to sync without the file. It was like a couple of days, to a few hours difference.

Keep thinking about this and maybe bootstrap file works better (faster) in POS coins because if I remember correctly, I have used it only for alts like Pivx, Dash, Bitsend, Masternodecoin and never in POW mined coins like our old good Bitcoin?