invisible placed blocks

settings include fast graphics, render distance set to 3 chunks, no smooth lighting, max frame rate, no 3d anaglyph, no bobbing, normal gui scale, no advanced open gl, highest brightness, no clouds, minimal particles, fulscreen on, no vsync mipmap levels set to 4. using these settings, i opened a creative world in custom generated mode. i began messing around with slime blocks. they would appear invisible, then appear after about 20-30 seconds. the i began using oak leaves, and they would not become visible at all. i didn't test any other blocks for an issue