I have an RPI5 connected to a PLC via USB to TTL-RS232 cable, where a Python application runs 24/7. The power supply is a 27W USB-C RPI official. I have the RPI OS installed and running on the SD card, although I have an SSD connected via USB, as I register some text files in the SSD very frequently (every 2 seconds). I have the RPI5 connected to an HMI (official RPI 7" touchscreen). RPI OS Bookworm installed is 64 bit version release 5.6 - April 2025.

After several weeks (around 2 months) of working perfectly continously (only a couple or restarts due to OS upgrades), yesterday I found the RPI5 freezed, it did not respond to anything and the taskbar was black. After disconnecting the power and re-connecting it, instead of having a normal RPI Desktop login, the RPI welcome screen stayed a couple of minutes. Then a black screen appears for some more minutes. Finally, the startup messages appear, where the following were not able to start:

[FAILED] Failed to start polkit.service - Authorization Manager. See 'systemctl status polkit.service' for details. [DEPEND] Dependency failed for ModemManager.service - Modem Manager. [FAILED] Failed to start dbus.service - D-Bus System Message Bus. See 'systemctl status dbus.service' for details. [FAILED] Failed to start bluetooth.service - Bluetooth service. See 'systemctl status bluetooth.service' for details. [FAILED] Failed to start snapd.service - Snap Daemon. See 'systemctl status snapd.service' for details. [FAILED] Failed to start udisks2.service - Disk Manager. See 'systemctl status udisks2.service' for details. [ OK ] Reached target bluetooth.target - Bluetooth Support. Starting dbus.service - D-Bus System Message Bus… Starting snapd.seeded.service - Wait until snapd is fully seeded… [FAILED] Failed to start systemd-logind.service - User Login Management. See 'systemctl status systemd-logind.service' for details. [FAILED] Failed to start NetworkManager.service - Network Manager. Starting NetworkManager.service - Network Manager…of a restart…ishes up…s…. 

Today, I have powered it up again, with the SSD disconnected, and something very similar has appeared:

[FAILED] Failed to start udisks2.service - Disk Manager. See 'systemctl status udisks2.service' for details. [FAILED] Failed to start dbus.service - D-Bus System Message Bus. See 'systemctl status dbus.service' for details. [FAILED] Failed to start polkit.service - Authorization Manager. See 'systemctl status polkit.service' for details. [DEPEND] Dependency failed for ModemManager.service - Modem Manager. [FAILED] Failed to start snapd.service - Snap Daemon. See 'systemctl status snapd.service' for details. Starting dbus.service - D-Bus System Message Bus… [FAILED] Failed to start snapd.service - Snap Daemon. 

After some minutes, the screen scrolls a little bit automatically and a terminal appears, where I am able to use the keyboard:

[FAILED] Failed to start udisks2.service - Disk Manager. See 'systemctl status udisks2.service' for details. [FAILED] Failed to start dbus.service - D-Bus System Message Bus. See 'systemctl status dbus.service' for details. [FAILED] Failed to start polkit.service - Authorization Manager. See 'systemctl status polkit.service' for details. [DEPEND] Dependency failed for ModemManager.service - Modem Manager. [FAILED] Failed to start snapd.service - Snap Daemon. See 'systemctl status snapd.service' for details. Starting dbus.service - D-Bus System Message Bus… [FAILED] Failed to start snapd.service - Snap Daemon. [ OK ] Reached target getty.target - Login Prompts. Debian GNU/Linux 12 raspberrypi tty1 My IP address is 127.0.1.1 ::ffff:127.0.1.1 raspberrypi login: biotagro (automatic login) 

Any guess on what the problem could be? I want the RPI to start always on desktop mode.

Is there any troubleshooting documentation that I can check?. I don't understand the error logs as I don't know how Linux works internally. Any clue about what to look for would be appreciated. My guess is that there is some problem with the SD card. However, I want to be sure of this, so in that case I mabye can install the OS directly on to the SSD.