Soyuz 4 and 5 (KSP 1.8.1/RSS/RO/Principia)

Soyuz 4 and 5 were the first Soviet spacecraft to rendezvous and dock, and also featured the first crew transfer between two spacecraft. The mission went as planned until the reentry of Soyuz 5, when the service module failed to decouple on schedule resulting in the spacecraft reentering nose first. Luckily, the service module separated before the hatch melted through and it resumed a normal reentry.