When you put up a weak defence team, you’ll be attacked by lower level players. I’ve had 1-trophy revenge PVP offers on people in the 30-50 level range. I’m around level 670. With all my kingdom and guild bonuses, it doesn’t surprise me that even the worst defence I could think of would sometimes catch a really low level player with a lucky streak and beat them.
Could be someone trying to use a really crappy team in PVP to complete a daily task, too.
Some of that is surely system crashes and disconnects, but you might be outright winning occasionally. Have a look at your battle log and see who is losing.
I put up a comic-relief defence team for a couple weeks recently and there was a level 1000+ player that couldn’t seem to beat it. I’d always check my battle log when it would get a win and this particular player was about 0 for 6 over that time. I still wonder about what was going on there…