Issue link: https://gitlab.com/ubports/porting/community-ports/android9/oneplus-6/oneplus-enchilada-fajita/-/issues/12

But this is likely to be caused by the reboot issue: https://gitlab.com/ubports/porting/community-ports/android9/oneplus-6/oneplus-enchilada-fajita/-/issues/6
There is a workaround mentioned, although it does not work for me (when I try to enable NTP time synchronization in Ubuntu Touch settings, then reboot).