Need help completing a challenge from Rise

I'm trying to complete the game at a 100% but there's this mission at the Soviet Installation that's making me go crazy. I remember not burning one of the posters the first time I went there and now I can't seem to get past it because it's closed. Does anyone know if I fucked up or if there's a way to get back there? The only thing left to complete in the Soviet Installation is that, I have 6 out of 7 posters.

https://preview.redd.it/wxkamtwd7z2h1.png?width=1359&format=png&auto=webp&s=a12c036e0b0fd34f664d52b2f72726f6eebd111f