Silvia tray is made from Stainless Steel and while pump is working, vibrations are transferred to the cups which start shaking, dancing and even moving across the tray.

All my efforts to slightly move/tighten the pump didn’t help. The vibration pump kept transferring vibration to other parts.

To absorb some of the vibration in the cup area of the tray, I took a silicone pipe with diameter of 5mm and cut 2 strips matching the tray ribs length plus 4 pieces of ~3cm length.
I cut each pipe in one side along its axes and attached it to the rib edge.

This simple addition stopped the cups dancing and also avoids scratching of the tray.
Another solution to this issue might be a perforated silicone mat (perhaps part of an iPhone skin/cover).