I am finally deep into my shower plastering project on the renovation we are doing. 3 showers came out fine with 2 coats of plaster so far. But the 4th shower is driving me mad. There is about a 3 foot circle section of durarock that the lime plaster will not adhere to. We've made 4 attempts at patching it and each time, the next day, the plaster is all cracked and comes right off the wall. The last attempt I used concrete bonding glue on the durarock, but it still did not adhere to it. The lower part of this wall and the adjacent wall is fine.
Any thoughts as to why this is happening and better still, any solutions?

Harvey:-(