hmm. well im having the same problem but mine doesnt crack. it happens everytime after i put my pole up. my ceiling doesnt have a flat finish its shiny, so it leaves a mark and i have like five different spots on my ceiling. however when i tried to wipe it away with a wet cloth, (i used one of those Clorox wipe thingies) it came right off. Try wiping it away if its just leaving a mark. if its cracking the ceiling, then that probably means that that part of the ceiling doesnt have a joist. If you want a way to find where the joists in your ceiling are, you can buy a stud finder which helps you locate the joists in youre ceiling , and then you can place it in between the two joists and you shouldnt have that problem. If you dont want to buy a stud finder, then you can try knocking on your ceiling: when it makes a solid sound, you’ve got a joist. when it makes a hollow sound, its empty. its making that semicircle because you probably have it under one of the joists only instead of inbetween two. well, good luck! =)