Nube you are referring to the horrible little spring contacts within the tail light. By "globe" you are are referring to the tail light lens. Nothing wrong with that. Different cultures, languages, different sayings and words. The British have their own sayings as well such as "boot" for trunk, "bonnet" for hood, "tyre" for tire, and "Lucas" for darkness.
Those springs are crap and haven't changed a bit from the ones on the 1950's Vespas I hate working on for the same reason. I swear I can mess with a person's tail light for twenty minutes, get it working correctly, and 20 minutes later the light will be out again. Bend the spring and it works for awhile.
There are 3 things you could consider,
1. Buy a new tail light. My understanding is that here in the States it is cheaper to order them from Harley Davidson as they used the same unit on some of the Buells, only difference is that the lens (globe) has a clear panel on the bottom to legally light up the license plate. These are really handy when doing a tail chop as you can ditch the little Ducati license plate lamp. I paid $45 US for mine.
2. You can drill out the lamp holder and install an aftermarket unit. I've done it a few times and it isn't an easy process, however it can work. My local auto parts store sells these generic 1157 bulb holders that have wires and a spring under them that push them onto the bulb. A much better version. Basically I drill out the original bulb holder and slide in the new style with some epoxy to hold it in place, then connect the wires.
3. Buy an aftermarket LED tail light set up for about $100 and it should last several years without any maintenance.
http://www.monsterparts.com/pc/TLDMON/Electrical/TLDMON.html