Yesterday I see in the wallet client something a little strange.
I open it (after some days), so it has to download the missing blockchains. When it has more thatn 1000 blocks to finish the download, it starts to generate POS bock, one after other for more that 100 POS.
That blocks where almost all confirmed and in the same time, when it starts to generate POS, in the pool there were all find and not confirmed blocks (some has 2 or 3 confirmations left) that goes orphans.
What is strange for me, it is that POS starts where not al the new blockchain was download and so my client was not syncronized with networks.
now I reopen it and with 2000 blocks to dowwload for syncroniation, it starts to make POS again (a block every seconds).
I've had what I believe is a similar problem to yours. When updating the client it "minted" like 50x in a day, but never added to my balance. On top of this, there are transactions from 2013 that are at the top of my list (being the "latest"), even though there are also a lot of 2014 transactions.