hi there, I hope someone here can shed some light on my problem. We have a white cesarstone counter top. The run is long, so there is a seam where the two parts connect. This seam has split a few times and the installer has come back to fix it each time, but its happened again. Why is it happening, is it humidity? He reinforced the countertop so its not sagging...not sure what to do. Please see picture attached.