This "bug" has been present for a few months at least. Only current selected tab is "forgotten" (after opening opera - says can't connect to servers/no internet). All other tabs are fine. Very annoying (I usually open few tabs at home there I have good internet so I can read them while I'm away, and I don't have access to internet there, so in order to save my tabs I have to open additional "dummy" tab and switch to it when I lock my phone).