Use a good quality pair of small jaw pliers [needle nose or ignition type] grasp the safety button and twist it slightly clockwise.
Check it and see if it's improved. Do this a little at a time, if you hurry or twist too far you will twist it off.
The button is attached to a flat piece that goes through the handle.
You are twisting that flat piece so it "rubs" against the side of the slot in the handle, creating friction.
Do a very slight twist and check to see if it's tighter. Repeat this until it improves. Once it's "just about right" STOP -close enough is good enough.
Italian makers have a tool for this. It is a small piece of thin metal with a slot in the end. It slides under the button and the slot slips over the flat piece that goes through the handle.
Cut a slot in a gauge set and you can use this as in the photo I have attached.
Also some guys use dental floss or thread and wrap it around the safety to add friction and so it does not scrap on the handle scale.
The "flat piece [or rod] of the safety that goes through the handle makes the friction or contact with the sides of groove for the safety rod that protrudes through handle this governs the tightness. Turning the part that protrudes (not top or actual button) slightly will cause more contact with the sides of groove than if the rod is parallel to the groove. By twisting clockwise it also forces the tab up to the handle scale and away from the liner making it tighter in the handle groove which is routered out.