If the script doesn´t work, check in syslog. If it stops at ` offline -> registered - .....` then your service provider doesn´t use NITZ and disconnections can´t be detected. You can use `atc-fib-fm350_gl_2024-04-24-0.2_all.ipk` instead, but you have to check network connectivity by your self.
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If you have problems with modem crashes this hotplug script may help to re-start the interface.