A common fault on the De is a failure of the door gas strut bracket. There was a batch of over length struts a few years ago which bent & damage the brackets. Age also plays a factor, as does driving with doors open and general faults in the tub manufacture at build.
A month or so ago I repaired Scott's car, and thought you'd like to see how to do it.
This is what usually happens
With the bracket removed you will usually find this.
Repairing the tub with glass fibre is very time consuming, messy, difficult to guarantee strength and the T & quarter has to come off!
So I made a template
Then a brushed stainless bracket with a smaller back plate with welded captive nuts, to fit inside the tub.
Sandwiched with Tigerbond to water seal it and held with M6 bolts, giving a much stronger and longer lasting support than original.
Making a nice straight strut mounting point.
Then put back together for an "invisible" repair.