Mintcoin was advertised as 20% for the first year.  While GetLastBlockIndex was returning the index of the last PoS block it was still 20%.  The only problem was when the wallets tried to transition to 15%.  The minting code was still trying to do 20% and the verification code was expecting 15%.
There was also an off by one, as you said.  The generation needed an Index+1 to get it into the 15% range.
Again there were never two chains so no fork.

There was no fork.  The chain just stopped until the 1.14 wallet was released, then it continued.  Old wallets will not be able to mint new coins, but should function fine otherwise.

Ideally everyone would upgrade to the latest wallet. I know some exchanges have been waiting because a couple wallets back the new wallet required the blockchain to re-download.

Not if you want to mint coins.  Old wallets will work for sending and receiving transactions but if you want to mint coins and support the network you need to update to the 1.14 wallet.

Yes, 15% for now.  If a majority wants this put back to 20% we can make that change.

Do you have access to Trello?  The wallet is under Desktop Wallet - Wallet Upgrade.  I do not have access to put it up on the google drive.

Ok, I am building the release wallet now.  I will place it on Trello when I am done.  I decided not to change the blocks per year number in the code for now.  Ee could put this to a vote on Reddit for the next wallet.  I just want to get things moving for now.

Windows build is now on Trello.

Love this response.