I think I've seen this before but only now confirmed it and worked out what's going on. If you fly a successful mission with something (the shuttle in this case) that's at Max Safety (94%) already, and there's a mission to go on the next pad, it gets Max Safety +1 (95%). This is all corrected by next turn - but it looks like the game checks for anything exceeding Max Safety after all missions fly.

I don't know if this is something that's worth addressing or not.