The "3120" schedule has issues that do not seem to affect the "4120" schedule. See that.

I.e., go to https://www.uio.no/studier/emner/sv/oekonomi/ECON4120/h18/timeplan/index.html . It is unclear - to me - whether this affects your "Mine studier" calendars (if you signed up for 3120). The administration is working on it. Nils