Noticed just about every Euro Tudor has the door sagging about 1 cm . Common with the old wooden frame door & body.
a local one i was looking at (admiring) had the same issue.sounds like the timber fading fast and the diagonal brace not holding rusty screws etc
on mine the door had a door tightener , a flat steel plate bolt across the door . i saw another one with the steel plate twisted in the middle to adjust the door , and another one with a mechanical adjustement . don't forget these bodys where hand built . have you see the doors back hinges plates ? hand made !