Reasons for big Difference between Vibe X & Y?

Hi Group, (std Quad-X config pixhawk fw333)
During view logs, I find a large offset between Vibe graphing of X and Y,
where X are within limits and Y appears ‘way-off’. I have inspected the
mechanic,

fc mounting -
A small frame is mounted on the crafts’ frame with hi density foam,
on this small frame is the suspension rubber bubbles, one in each
corner. The bubbles connect to another small frame on which the FC is
mounted with d/sided rubber.

This assembly use to give me very good Vibe graphs.

However, now it is ‘off’ as explained above.

Can someone please assist or give me advise on this?

I have inspected the mechanics
Used different props, balanced,

Same results.

I posted similar enquiry here, including pics and .bin file.

Thank you for reading this, I am looking forward to your insight
and advice.

Regards,
Gerhard