Was not able to reproduce the issue.

Please make sure that the instrument is inserted into the ground and that the correct instrument is selected on the left side of the HUD.

Simply click where it says "INST" and then select the "PROBE 1" instrument from the list.

I did, it showed the analysis results page but the task did not disappear.

Are you sure you rotated the arm's head in the right direction when using the probe? Please attach a screenshot of the robotic arm so I can see if you are positioning your arm correctly.

I compressed the image a bit too much, you can kind of see the probe in the sand. I can upload a better one but I can't work out how to delete the current one.

It seems (its kind of hard to tell) that you are putting your drill into the ground, not the probe. The probe is located an a different side of the robo arm's head. Try rotating the arm's head with the PROBE 1 instrument selected.

Note that saving the screenshot as .jpg should be quite enough to reduce its side. Compression should not be necessary.

Got a better picture up, really sorry about the other one. It can't be the drill because I haven't unlocked it yet and I'm not playing scenarios.

Can you please add a screenshot with the objective marker visible? Please make sure you can see the title of the marker as well. If you could display the mission in the mission tab of the hud that would be great!

The problem seems to have fixed its self.