Glitchy half slabs

I've been building a lot with half slabs recently and often see the texture glitch to a double slab or oppsite slab(top/bottom) but with like a hole like some sides of the texture stays in the right place or something-- also when holding them occasionally it would appear a faint animation as if im picking one up. Im building in and on an ocean, not sure if that would make a difference or not. To recreate i suppose just sorta build or play with them and keep an eye on them. It seems random with no way of predicting reoccurance.