Missions can be dropped and retaken via the journal, however each missions is usually broken into sections (space, then ground, then space etc)
if you do something that is truly mission breaking to the point where you cant continue or it bugs out, if you leave, wait 5 minutes and re-enter you will just start at the last section you were at, so no need to replay the whole thing.
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btw, what do you mean by botched anyway?
if you have not completed the mission, just go back in.
or, drop it and re-select it.
or... if completed, episode replay.
oh, i think some patrol missions might be once only.
if you do something that is truly mission breaking to the point where you cant continue or it bugs out, if you leave, wait 5 minutes and re-enter you will just start at the last section you were at, so no need to replay the whole thing.