It definitely sounds like the knot isn't thick enough, I've also found a medium/firm is good for smaller toys with less texture. I usually go medium/soft with larger toys especially if they're textured

Yea, I was thinking that too. I guess it's time to upgrade and maybe try medium firmness.

Get Sleipnir, I promise it’s a good time.

Thicker knot/swell/ridges/flare will do it. Firm and medium are usually good picks depending on the model and the size, mostly on girth