Vinyl siding panels that have been repainted sometimes warp or buckle.
What Causes It?The most likely cause is that the vinyl siding was repainted with a darker color paint than the original color. Dark paint tends to absorb the heat of the sun, transferring it to the substrate. When vinyl siding expands dramatically, it is not able to contract to its original dimensions.
How to Solve ItPaint vinyl siding in a shade no darker than the original. Whites, off-whites, pastels, and other very light colors are good choices. Top-quality acrylic latex paint is the best type of paint to use on vinyl siding, because the superior flexibility of the paint film enables it to withstand the stress of expansion and contraction cycles caused by outdoor temperature changes.
Siding that has warped or buckled should be assessed by a siding or home repair contractor to determine the best remedy. The siding may have to be replaced.

Note: Images provided by The Rohm & Hass Paint Quality Institute.