I do a lot of lamping for rabbits and Fox.
first of all get yourself another torch for scanning and carry the rifle on a sling.
This is a lot safer and will also reduce the fatigue of holding the rifle for scanning.
As for the rabbits running before you can get the shot, this could be a few things but difficult to diagnose without seeing what you are doing.
They could be seeing you, hearing you or winding you.
They could also be getting lamp shy, but still, good field craft will help.
Move quietly and practice getting the rifle onto the sticks without making any noise.
Move into the wind or with it crossing so they can’t wind you.
Remember that their main senses are hearing, smell and ground vibration. They are also not blind.
Watch your background so you don’t get skylined.
I hope there is something there to help you or maybe you already know all this.
Good luck and remember to have fun.