No connection to printers

What is the problem?

After using octoprint with my 3 printers for years, I run into problems connecting to any printer.
Restoring backup from 2021 -> works
Updating Octoprint -> works
Updating python 3 -> again no connection possible

What did you already try to solve it?

Tried to restore backup and bring it up to date.

Have you tried running in safe mode?

yes

Did running in safe mode solve the problem?

no

Systeminfo Bundle

You can download this in OctoPrint's System Information dialog ... no bundle, no support!)

attached
octoprint-systeminfo-20250121163524.zip (43.8 KB)

Additional information about your setup

OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ... as much data as possible

printers 2x CTC Makerbot Clone, 1x self-made mks board, PI4

Changing monitoring state from "Offline" to "Opening serial connection"
Connecting to port /dev/CTC, baudrate 115200
Changing monitoring state from "Opening serial connection" to "Connecting"
Connected to: Serial<id=0x9c64b050, open=True>(port='/dev/CTC', baudrate=115200, bytesize=8, parity='N', stopbits=1, timeout=10.0, xonxoff=False, rtscts=False, dsrdtr=False), starting monitor
There was a timeout while trying to connect to the printer
Changing monitoring state from "Connecting" to "Offline"
Connection closed, closing down monitor