was it against the same target?
because from what i know, raiding chance depend on the crew count on each side, maybe the later targets had more crew?

same target, after I posted this, I succeeded in raiding him once, and have failed twice since then (I think I'm either unlucky, or he's got roughy the same crew)

think of it as a die being rolled each time you attempt....
if the die rolls high enough, you succeed
if it doesn't roll high enough, you fail

the chance of success depends on your raid strength (your crew, and raiding modifiers) vs the opponent's raid strength (their crew, and ...possibly raid modifiers as well)
....this equation is mostly hidden from us because all we learn from an attempt is whether we succeed or fail....
....i suppose if someone had 10,000 time manipulators on them, they could record repeated attempts and give us some sort of percentage w/ a degree of confidence... but... that's never gonna happen (unless binaryman wants to accept that project)

anyways... the point is.... it's just weighted random chance...

another way to think of it would be like having a quarter with a dry spot of glue on one side, near the edge, making flips less regular.... you'll sometimes have streaks of heads and streaks of tails, and sometimes it'll flipflop heads tails heads tails... but in the long run you have XX% chance of getting heads and (100-XX)% chance of getting tails...