I was making a automated wool farm and I was using a dispenser full of shears to shear a sheep. It happens that dispenser doesnt work... even with a button it doesn't react! In attachment goes a video of the issue.
MC-156264
Dispenser with shears doesn't shear sheep
Resolved
Invalid
0
Your dispenser block is already redstone powered and therefore doesn't get powered again.
This is not a bug - you didn't build it correctly.