If you set a command on command block and reopen command block's interface, you can't see the command you set.

You can see this bug with following steps.

Step1. Place a command block.

Step2. Open command block's interface (Right-click the command block).

Step3. Set any command.

Step4. Close command block's interface with "Done" button.

Step5. Open command block's interface.

Expectation: Command block's interface show the command you set at step3.

Result: Command block's interface doesn't show the command you set at step3.

Note: Command that you set on command block works fine.