DM6 with ghost hit

Hi guys! After all, sorry about my poor English. I'm Brazilian.
I acquired an Alexis DM6 and it was used. The device was ok, but I realized that the tom2 sometimes was hitting by itself. It's wasn't happening all the time.
After some time without use, my oldest son started to use it. Today, I went to practice and realized that the share and the rim was being triggered when I hit the hi hat. I hit sometimes the black screw that fix the hat to check if the vibration was doing it, and looks like that's it.
Could someone help me how start solution it?
Thanks a lot
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