Martin, place a piece of paper on the door sill and close the door to confirm your suspicion about what is causing the noises. Over the years the doors may have sagged slightly, so loosen the hinges and raise the doors maybe 1/16" to see if the noise disappears. Be sure to trace around the hinges before loosening any bolts so you know the original location of the hinges in the door frame. Also, be sure to have at least one person helping you when adjusting the door position because the door is quite heavy and unwieldy.

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Fred Hoelzle