I’ve studied my case a bit further when I got second time this issue;
- Happens now every time phone goes to roaming network
Somehow phone refuses to accept 4G eventhough it is available.
I think I have a success recipe now for my case:
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Stop ofono and delete its folders as Jolla instructs (trick nr 3):
https://jolla.zendesk.com/hc/en-us/articles/115011870727-Resetting-oFono-settings-to-make-mobile-data-work -
Shutdown phone
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Do the “Sony reset”, while phone is shutdown hold both volume buttons pushed down and at the same time push power button as long as you feel three times vibration. I don’t know if this step has a relevance or not, but it’s not so big thing to do either.
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Switch another SIM card into the Sailfish phone
Play a bit with internet, for example browser
Shutdown -
Switch back the original SIM card, start the phone
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Mobile data revives and phone accepts 4G again (…until I go to same roaming area again)