Yesterday I completed 8 (well 9 really, explain at the end*) Salvage Missions, all from Wreckage or Crash Sites. All done without any problems & rewards were collected on completion.
*When stacking 3 Salvage Missions, 2 on one Planet & 1 on another, I was puzzled to notice that after clearing the single Mission on the Planet, the Panel was showing a second 'blue' highlighted Crash Site. On visiting this Site & retrieving the Item, I got the Mission completed message on the HUD
.
Though on handing in the Missions at the Station there were only 3 showing on the 'completed mission' screen............maybe the game remembered one of the Missions I abandoned the day before
.
Big improvement though, now I can go back to hunting out the rewards I need for my upgrades
.
*When stacking 3 Salvage Missions, 2 on one Planet & 1 on another, I was puzzled to notice that after clearing the single Mission on the Planet, the Panel was showing a second 'blue' highlighted Crash Site. On visiting this Site & retrieving the Item, I got the Mission completed message on the HUD

Though on handing in the Missions at the Station there were only 3 showing on the 'completed mission' screen............maybe the game remembered one of the Missions I abandoned the day before
Big improvement though, now I can go back to hunting out the rewards I need for my upgrades