When the lava flows by 4 blocks (the maximum) and the water comes into contact with it, it is not generating a cobblestone.
This affects 0.13.0 build 4 On Asus Zenfone 5
Steps to Reproduce:
1. Create a hole 6x1.
2-Place lava at one end and allow to drain for 4 blocks.
3-Put water at the other end.
4 Done. The water will come in contact with lava but will not be created one cobblestone.