Unable to remove lead from mobs

I found a bug, where when I use rope and tie animals to each other (rope technique) it cannot be removed, and the animal must be killed first before the rope can be removed. Then when you tie the boat to the happy ghast, it can't be removed, it has to be killed first. I have accurately aimed the cursor/aiming and am already in a crouching position, but the button does not appear, so please fix this bug immediately, hopefully it will be fixed soon because this is very important!