Can't get past Allied mission 9 (Leningrad - The Moon Shall Never Have Them)

TL;DR

Every time I win the mission, the next mission turns out to be the same as before (mission 9). I can't get to the next mission (mission 10). Why is that, and how do I start the next mission?

---

I'm trying to finish the Allied campaign of Red Alert 3, but I'm stuck on mission 9 (Leningrad - The Moon Shall Never Have Them).

After I destroy the launch facility, I get to see the victory screen as well as the mission timeline. When I click on continue, I expect to see the video cutscene introducing the next mission.

The problem is, I'm seeing the exact same video cutscene as for mission 9. When the cutscene is finished, the briefing for the next mission is the same as for mission 9, and when I choose to start the mission, it's the same as mission 9.

So I decided to load a previous save. Unfortunately, I only had Autosaves, and the latest one was from when I started building my base, so I had to essentially replay the mission from scratch. After winning for the second time, I still got the same cutscene and briefing as before.

I'm effectively stuck in a loop where I keep doing mission 9 and can't progress to the next mission. I can't find anything on the internet, so I have no clue how to fix this. Any ideas?

Just in case this bug is triggered by my playstyle, here's how I finish the mission:

• Playing on Easy
• Building defenses to keep Soviets out of my base, leaving the Mirage Tanks behind the defensive structures.
• Building Proton Cannon to shoot the Iron Curtains when ready.
• Building 4 Airports and filling each one with 4 Vindicators to continuously bomb the Iron Curtains.
• Occasionally dropping Time/Deluxe/Supreme Bombs and Surgical Airstrikes.
• Repeat until mission is won.

What could be the reason I keep playing the same mission over and over again, and how can I get past this loop?