An issue regarding lines on the projected image is very often caused by dry joints or bad contact on the main board of the projector. This can arise through overheating. Almost every problem on a projector is caused by over heating. Lamp failures, lines on the image,missing pixels and randomly switching off are all symptoms of over heating.
If you push the top off the projector the lines will often disappear although this is not recommended. Quite often some of the chips on the board will need to be reflowed especially the 8 legged integrated circuit chips. The problem also occurs very close to the DMD chip. The DMD chip gets very hot on an Acer projector. So hot that its has its own heat sink with special paste to cool the chip down.
At Acer projector repairs we charge £99 to fix this problem and have around a 70 percent chance of repair. Sometimes though an new motherboard or second user board is needed to fit it.