Today the bricklayer was supposed to knock off loose plaster on the facade to improve it where needed. On one gable, it turned out that the bricks were loose under the plastered facade and the mortar between the bricks was crumbling completely. The visible crack has been noticeable as a line in the plaster for the five years we've lived here and according to the previous owner family (who have had the house since the 1940s) "always been there." The house is from 1889.
Does anyone have suggestions for measures?