Gantry bar upgrade - vibration/shaky

I ordered the 1 piece x-axis gantry from Inventables and put it on last week. It’s way stiffer, but I’m seeing a vibration/shaking when the gantry is in the middle 3rd of the axis that I’ve never seen before,is this normal? It gets smoother as it approaches either side rail. It is more pronounced at faster speeds, too.

I’ve gone back thru and inspected and reinspected the v-wheel tightness and they seem to good. I tried tightening them a bit and then making them a bit looser than normal and no difference. Rechecked the screws holding the bar on, too. Any idea’s what is goingon or is this normal?

Thanks.

ridges look fine. The belt did seem a bit loose, so I tightened it a bit, but still does it. If I loosen the v-wheels, it goes away, but then they’re too lose. lol

When the gantry moves at slow speeds, it does not happen. I’ll just keep tweaking away at it and see what happens.