Hairline Crack Keeps Appearing in Ceiling Even After Repair

[PeterJ]

I have had a ceiling skimmed but a hairline crack keeps appearing. I applied a coat of polycell ceiling crack paint with good results. However I Needed to apply a second coat and the crack reappeared. on close inspection it appeared that the paint had been squeezed out of then crack and formed what looks like a very fine bead on the crack. I sand the area very lightly and applied a third coat, but the outline if the crack reappeared. Any ideas please?

[PeterJ]

I have had a ceiling skimmed but a hairline crack keeps appearing. I applied a coat of polycell ceiling crack paint with good results. However I Needed to apply a second coat and the crack reappeared. on close inspection it appeared that the paint had been squeezed out of then crack and formed what looks like a very fine bead on the crack. I sand the area very lightly and applied a third coat, but the outline if the crack reappeared. Any ideas please?

By way of clarification the crack seems to be the joint between plaster boards. The crack was scrimmed prior to being skimmed. There does not appear to be any structural movement. I was thinking of sanding down the general area of the crack and repainting with the polycell product again. I am undecided to either use a brush or a roller. Have used a roller prior to this but surface is getting a bit orange peely. Any advice would be appreciated.

[HandyMandy]

Is it worth maybe sanding down polyfillaing drying, sanding then redoing? I may have misunderstood what your are saying though.