After doing an escort mission to serco land, i was making my way back, and took a short mission that was literally one system jump, there was no problem and it got me closer to home.

We all arrive at the station sedina mining - and ships start to ungroup except for the frigate that also is right outside and looks in no condition to dock with anything.

I leave aand re-enter the station but nothing happens so i abort the mission. - should i have waited in station or in the nfz where the big ship was or is this a bug?

The frigate should leave the group (docking from the perspective of the mission), about a minute after entering the destination sector. Did you wait at least that long before aborting?

yes several - good to know for next time that serco large ships are commanded by morans.