[The Rovering Member]

On my replacement aubergine panels I used spray adhesive up through the hole where the handle goes & it worked well for a time but in places it's now loose again.
As already said, the disintegrating foam backing is the problem so the solution is a fairly straightforward but time consuming one. Remove the covered panel from the main door casing & replace the foam backing.
Depending on personal taste you could also change the covering too. l wouldn't but it's a possibility should you be so inclined.
Actually my original black door panels weren't sagging so l could do a straight swap rather than strip the covering.