Minecart network and tracks unusable

Since last week snapshot (15w41a and b), all my minecart tracks and network don't work, I end up getting kicked out of my server whenever I use it, seems that the minecart goes too fast after a few booster rails (every 29 blocks) and the chunks aren't rendering anymore. Please do something about this, its getting pretty annoying since my world is extended and walking (since horses aren't rideable either) is getting quite annoying and consume a lot of food.