ML Ascent that distorts

Dear all at MLO.

Hope you had a great Xmas time.

There's been some time that I don't visit the forum, but now I need help from you, so, sory to bother

I'm a proud owner of a pair of Ascent's, that I bought 2nd hand/ ex-demo about 4/5 years ago.
Now, suddendly, one of the speakers became generating a lot of distortion in some of the frequencies ( i.e voices, snare drums) but only when I play at a moderate to little high levels, but it still performs great at low levels.
I have changed the speakers from left to right and reversed channels on the amp but it still distorts.
The serial number for the Ascent's is NSNA 476/477, being the one with this problem the NSNA 477.
Could you please be so kind as to help me with any kind of advice on what should I do or what might the problem is?

Many thanks in advance

Best regards

David

Can you describe the distortion better? Can it be a loose connector or loose screw inside the cabinet?
Can you isolate the distortion to the panel (by leaving the woofer unconnected), and is it the whole panel or only a portion of the panel distorting? Does the distortion change in character when you squeeze the panel together (ie, is the ESL sandwich separating and causing a buzz)?