Blocks break after some time / Items spawn in after some time

After i joined the Server the first time there where Wool and Saplings on the floor. Then i started flying around and saw Sugar Canes in snow biomes which broke after some time of doing nothing. I recorded a piece of the Bug inside this video: http://youtu.be/S6AUTo5k4wI?t=1m6s after 10-15 seconds the first and the second Sugar cane broke without doing anything.