Unibond (PVA) the wall where the crack is and bed two layers of scrim tape over the crack put another coat of unibond over it and let it all "firm up" When it is solid get some easi-fill and feather it out from the architrave a few inches then let it all go off then sand it carefully so it blends in with the wall surface being careful not to go thru to the scrim tape. And before you paint it put a line of caulk up the wall and architrave and feather it out with your finger. Jobs a good un'...
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