Alright, this is pretty much a reply of episode 3, but Ubisoft released a patch for the private beta which may or may not address one of the known issues they talk about on their website, which is as follows:

We are aware of issues causing players’ game client crash on Xbox and PC after an extended gameplay session while PS4 players may experience a performance degradation after 3+ hours of uninterrupted gameplay. To circumvent both issues, we recommend players to restart their game client every two to three hours.

So hopefully it’s all fine now, but it means replaying that level again – albeit with more experience this time – and I feel more like I know what I’m doing now, and I’m able to get through it more quickly and actually defeat Saint this time with Agent Kelso.