Had a couple of jobs where the customer has studded out and boarded a former doorway in a masonry wall. I've scrimmed the joins and skimmed the wall and have had a couple hairline crack on the join. I've also seen the same thing on jobs I haven't done, so it's not just because I'm a bodge! (Unless they are bodges as well :RpS_bored
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any tips as to why this happens and how to avoid?

any tips as to why this happens and how to avoid?