FORD 6006e security panel keeps falling out!

I have a Ford 6006E

It has a warranty sticker which says Jan 08, will it be covered under the
warranty

It is not the stereo that originally came with the car (that one was
stolen)

I was told it was bought off ebay and fitted by the previous owner

Firstly I was told the warranty would cover it, but now they tell me it
'might not' ?!

The problem is.....

The security strip / panel won't stay in on my unit. You can sort of get
it to stay in (not properly it still sticks out a little) but then if you
go over a bump in the road it flies out!
Somehow it doesn't seem to want to click in, i.e. the unit is not be
gripping the panel on the left hand side (by the button)
The button also doesn't pop up like it should
I have tried buying a new security panel which did not work, so it makes
me think the button is faulty.
Hope you can help!