How have you asked for him to stop messing with the bit? Maybe he is messing with the bit because he has not been asked to do any differently.
Doesn't sound like he dislikes this bit. Sounds more like he needs to be taught not to mess with it. He might do the same thing with any bit you try.
Not that I'd recommend this bit for regular use, BUT, you might try a very high ported walking horse bit and don't fasten you reins to the shanks, but rather fasten them as close to the bit as possible. Some bits have a ring for this purpose. This will give you an indication of whether he is playing with it because he can, or it's the bit bothering him.
And be very careful, some horses will not tolerate this bit at all. Do some ground work with the bit before trying to ride him.
I sometimes really get amused at how we classify a bit because of it's name, and have probably never tried one. The verbage "double twisted wire" sounds harsh. But stop and think about how it is made and how it works. A double twisted wire is as close to a straight bit as you can get, but it has give. The horse's tongue is not forced into place. The joints on a double twisted wire bit are staggered to allow for movement, but not pinching. The wires are smooth so there is nothing sharp resting on the bars. It is much milder than any single( or double) jointed snaffle. The snaffle is a tongue masher, and normally makes for a hard mouthed horse. And remember severity is in the hands at the end of the reins. If you have never started a horse with one, don't knock it. It will work with almost any horse and do a much better job than any snaffle. If you say the professionals use it on hard mouthed horses, they could also use any bit for the same purpose if the hands get rough. Guilherme
, have you ever started a horse with a double twisted wire? If not, how can you have the opinion you expressed? My statement is from experience and actual use.