Doesn't Show Command in Command Block

The command in the Command Block wasn't shown

What I expected to happen was...:
To see the command in the Command Block

What actually happened was...:
The command field of the Command Block was empty

Steps to Reproduce:
1. put repeating command block on the floor
2. Enter this command: /tp @p ~ ~1 ~
3. Set Needs Redstone to Always Active
4. Exit the Command Block
5. go around till your going up and down smothly
5. try open the Command Block
6. often the command isn't shown