Gregory's Server@farbenstau The question is:
Does "meist" become always when it's done properly and it's a failuire to do properly causing the meist?
Or is it always random?
I think the concrentation of such defects in particular orders for particular installation kinda speaks against a truely random "meist"? However in east germany "concrete cancer" also impacted some "Plattenbau"s but also in local clusters. 🤷
@freemin7 To me, it sounds like you cannot rule it out completely, either due to the source material being too heterogenous in nature, or due to factors that are not completely known/understood yet. So you need rigid quality control, both during manufacturing and at regular intervals once the sleepers are in place.