A fast redstone clock connected to a commandblock does not give an output.
Related issues
Attachments
Comments

[media]

can you please add the code you used?

this is not a bug(if i think), this happens in other versions to.
try making the redstone wire from the clock to the command block 4 long instead of 1 long

when the comperator unpowers itselve it still has an output of 2, so the wire to the commandblock must at least be 3