ok I found the problem and solution.
I completed the Stug 4 mission without finishing the light missions, I did the other 4 with honours so no need.
if u haven't completed ALL the previous mission sets then the mod auto takes u back to them.
u can turn this "feature off" by editing the following file
\res_mods\0.9.6\scripts\client\mods\quests_extended.xml
and changing
<IgnoringFinishedSeries> true </IgnoringFinishedSeries>
to false, this will keep the quest in the same mission set