Bootstrap.dat stopped synchronizing


I am trying to retrieve my litecoins from backup storage after 3 years or so. I installed the latest litecoin core wallet (13.2.1) and downloaded the latest bootstrap.dat and verified it. The problem I am having is that it stopped synchronizing with 31 weeks to go.

Do I have to import my old wallet.dat file first for the synchronizing to work? Or can I do it later?
edit: tried it with the old wallet.dat, it still isn’ t synching completely but I see part of my transactions now.

Any ideas what I can do next ?