MX7000: Standby Management Module (MM2) Stuck in Initialization and Firmware Mismatch Issues

We have an MX7000 where the MM2 (standby) stopped working. We purchased a new MM to replace it, but the new module remains in the "Initializing" status and does not move past this message in the GUI and the front panel.

There are also two errors related to MM2 concerning firmware mismatch and lost redundancy, as shown in the image below:

Additionally, there are two more errors in the logs that may be relevant in this case:

I attempted to update MM2's firmware from MM1 via the GUI, but it failed:

Using PuTTY over SSH, I tried performing a failover, but encountered the following errors in both PuTTY and the GUI:

Using a serial cable via PuTTY, I can access the system, but the prompt to enter the username and password does not appear:

The status in the GUI shows standby with a warning.

Thank you in advance.

Norian.