As you can partly read on TJC, I have tried this and reproduced the bug with multiple operators with different SIM cards (Czech, German) in multiple countries (Czech Republic, Germany, United Kingdom) on multiple devices (2x Jolla 1, 1x Jolla C).

It began with the first early 2.0.1.x release and happens mostly on 4G (it happened couple times on 3G as well, but that was an exception). It started right after upgrading too, so there is a clear connection to the upgrade and its regression (I also tried on freshly reinstalled devices, so apps/old configs are not to blame). Restarting the device doesn't help, restarting the network through Sailfish Utilities doesn't help, only switching from 4G to 3G does. Therefore I have been on 3G last half a year.

It's not like it's some weird coincidence - Jolla have acknowledged the problem (see the Tracked by Jolla status), but has yet to fix it. I suppose there are still many people who haven't gotten their 4G SIM cards (I know a few) so I suppose that's one reason the bug report has 'only' 35 votes.