FAF Coop Campaign "Meltdown" issue

[MorganF]

Hello everyone!

I've been having some issues with the Coop Campaign map "Meltdown" recently. More specifically, the problem is that stage 2 of the map never begins, because not all objectives or marked buildings have been destroyed. This is rather strange, since all marked buildings have been destroyed, as you can see in the screenshot.
I first encountered the issue yesterday as I was playing with a buddy of mine, and we ended up just quitting.
I gave it another go this morning, but the same thing happened. This time, though I checked the objective marker in the corner of my screen before giving up, and it showed only 14 of 19 objectives destroyed. So, watching some older Youtube-replays of the same campaign, (I get an error when trying to load the replays listed on the Coop Ranking list) I could see that the objective only had 14 markers.
I took to Google to see if this was a known issue with a known solution, but could only find 1 other person who reported the issue back in January: viewtopic.php?f=3&t=8618&p=91845&hilit=Meltdown#p91845
It seems that his issue is the exact same as mine.

I'm on a Steam installation, since my DVD drive won't let me install from the DVD, and I'm not using any mods.

I've attached a screenshot to show the 14/19 objectives and the replay ID is 3248150.

Regards