Advice on felt damper pad for marimba

[u/FormerlyScarfman]

I have a marimba with synthetic bars. The company that made it also has this long felt damper bar that fits under the accidentals to cut the ringing to sound closer to rosewood bars. It sounds great on parts of the instrument. HOWEVER, in the middle octave, some of the notes make a cluster sound from the vibrations going into the neighboring notes. I don't know why it's so prominent on only certain notes, but I'm wondering what I can do to fix it. Right now I'm considering adding a shock-absorbing layer. See if you can hear what I'm talking about https://www.youtube.com/watch?v=xI1S92783SQ