I now see what's happened, I have replaced the enemy corvette with a laser frigate which does not have explosive decoy launchers.

Here's a video demonstrating the issues with that level: https://youtu.be/uxPsiDvRgfw

First part, all 3 ships have power disabled, yet the ship isn't considered disarmed till those launchers are destroyed. In this case it satisfies the victory condition at the same time as the failure condition.

Second part, the glitchy encounters I was talking about, and then the mission failing when those launchers take the rest of the ship with them.

@SoulWager I passed missions by setting destination fleet as main body, so I didn't manually adjust main body in the editor. Now main body in mission 4, 7, 8 has changed to Sol, orbits should be fine now.
As for mission 5, I passed it without destroying all decoy launchers, so I didn't encounter the issue you mentioned, sorry. screenshot for mission 5 passing again a few minutes ago

Missions 7 and 8 also have broken orbits. Did you even play test this?

Mission 4 has wrong object set as main body, breaking orbits.

Mission 5 has glitchy encounters, and ships with decoy blast launchers that kill their crew when destroyed, but which also must be destroyed to pass the mission. Shouldn't be required to cheese the AI for twenty minutes to get it to spend all its decoys just to be allowed to disable it.

Loading into the Mission select screen works, gonna check the missions later. Hopefully i can beat em^^

Thanks for feedback, I've attempted to fix the bug, check whether it's fixed or not. (I also ruined the description, gonna rewrite it later)

Sadly thats also true for me, would have loved to play it.

same here, it crashes my game

It crashes my game for some reason