If you place one command block and put a command in it and if you die and press respawn button you will see that the command block is no longer working and if you right click it GUI won't open.
Linked issues
Comments
this is already fixed in 15w37a
MC-88354
command blocks not working adter death
Resolved
Duplicate
0
thvardhan
(Unassigned)
Unconfirmed
Minecraft 15w36d
Retrieved
After death not adter its a typo sorry but I don't know how to edit it