How can I repair crumbling tile sealant?
Let me see if I understand: Your kitchen wall is covered with ceramic tiles and the "sealant" is actually grouting between the tiles, right, and now grouting is falling off? If this is the case my first guess is that grouting mass was old (wasn't used before expiration date).There could be some other reasons like poor workmanship etc. On of this is really a big deal, I mean it's not anything serious. What you should do is clear with some sharp tool existing grouting and apply new one. Material is not expensive, and you can do it on your own, because it doesn't require any special skill, just follow the manual.