At the official source code wallet there are some problems with the syncing. After block 1 000 000 (block when mining finished) there is problem while syncing. It is needed to restart wallet few times. After that syncing will continue.
Another problem follows: syncing after block 1 000 000 needs more and more time for the syncing the same number of blocks, it is slowing down exponentially and that should be corrected as much as possible and plan is Melite should sync as fast as Novacoin and Peercoin, taking into account the number of blocks.
I am trying to find the cause by changing the source code step by step, looking at and comparing Melite source code with the 5, 6 PoS coins, especially comparing with Novacoin and Peercoin from which all PoS coins originate and more or less share the same source code basis (I could say the diffewences from the Melite source code are big). This process of changing the source code is very slow, I am playing with that more than 2 weeks.
Also, I have also synced and still syncing the blockchain so many times while testing (from the beginning, from almost the end, or many times from somewhere between).
At this moment conclusion is: when you notice the blockchain stopped syncing, you need to restart wallet and continue syncing.