Block explorer shows there are lots of empty (zero reward blocks) - you can check that here:
http://45.63.119.167:3002/ - those are the blocks not shown in the list, but are searchable - for example block 4815.
The only explanation I find, is
someone is mining this via PoW (with zero rewards though
)! Who is that? Did the developers switch ON a miner and forgot that?
That could be one of the reasons many wallets do not stake for a long time, as PoW steals the blocks.
From what I see in the wallet:
Current PoS difficulty is 3.68216
Current PoW difficulty is 0.0621106
The other reason is the wallet with massive amount of coins, which is definitely stacking the most. That wallet will be deactivate soon (cit.).