I’ve had it fail multiple times in a row too, but my dinos most definitely dodge more often than before. It’s only expected that the more times you use it, the more times it’ll fail.
I don’t currently run any creatures that rely on stunning a lot, but I would like to point out that evasion is put to the test way more turns per battle than stunning moves are. If you were to use back-to-back stunning moves the way there are back-to-back evasion moves (e.g. Evasive Stance) you would probably notice it failing more often.
A similar effect is seen in the tournaments, where you need to grind battles in bulk, so the number of times you fail for the same probability increases. I remember in the epic tournaments a long time ago, when everyone ran the likes of Sinoceratops (pre-nerf), whenever I faced an opponent that also had one, I would often use the slower stunning move in the hope that their stun would fail. And that strategy worked way better than it had any right to.
Similar story with Stegoceratops (again, pre-nerf).
The more you battle, the more times RNG’ll fail you and your opponents. It’s why there’s been so many threads about RNG being rigged whenever there’s a tournament running.
I will not deny that this can be extremely annoying, and my sympathies to everyone who’s ever been consistently unlucky in a tournament before. Just remember that you’re not the only one.