To be honest, I have always found that simply tightening the main hinge screw slightly on both sides sorts this out by making it pivot a little more stiffly. The screws themselves gradually tend to unscrew themselves over time.

Be aware that the bottom two screws on each side loosen at the same rate as the main one, so if you discover that the top hinge screws are already loose, do them all up at the same time, or locktight the lot of them (blue/non-permanent loctite). You will need jeweller's screwdrivers, size 0 and 1. Don't use the size 1 on the bottom screws (which are smaller) as you will damage them.

If all the lower screws come out, then the handle is no longer supported correctly and will twist unevenly around the pivots. This will cause the handle to break, eventually.