you well know i do agree on this issue
these cars were hand made, in some sense they are pre-industrial (bear in mind that despite what it says in the front emblem, they are NOT BMW, they are KARMANN), so almost any part (with exception made of mechanical, engine, and so on), needs fine tuning prior to assembly, and then a lot of work to final fit
it is not a matter of throwing the part on its location hoping it will automatically fit there, this will NOT happen !
my last experience on the RH door is a perfect example, 5 weeks of after dinner time work (roughly speaking 70hours) and just finished !