As I have explained in several other threads... it isn't that your password has been change or stopped working... it is just a "bad" error message being output by the application.
The easiest recovery is to simply install breadwallet on an Android or iOS device, restore using your MultiBit HD seed and you should have full access to all the funds that were in your MultiBit HD wallet.
Alternatively, if you use
my python scripts... specifically the find_unspent_multibitHD_txes.py script, you will get:
1. a list of the UTXOs in your MultiBit HD wallet, along with a list of the matching Addresses/Private Key(s) for these UTXOs
2. a plain text output of your wallet (parsed_wallet.txt) NOTE: all seeds/private keys are still encrypted in this file.
My investigation into the source of this issue leads me to believe that newer transactions are unable to be parsed correctly by the wallet. This manifests as a "Transaction did not deserialise completely" message in the application debug logfile. Unfortunately, the wallet does not handle this error properly and returns with the "Password did not unlock the wallet" error
If you need any help, PM me...